IACS Institutional Repository

Front Title

Dutta, P

Duorah, K

Duorah, H L

Indian J. Phvs. 82 (6), 673-678 (2008) 
Nucleocosmochronology of Dergaon meteorite 
P Dutta1*, K Duorah 2 and H L Duorah 2 
1
 Department of Physic*, Dimona College, Khetri 782 403 Assam India 
1
 Department of Physics, Gauhati University, Guwahati 781 014 Assam India 
E-mail pratima_dutta2005(<» yahoo com 
Abstract By considering relative abundance ratio of ^K / ^Ar in Dergaon meteorite we have estimated age 
of the Dergaon meteorite as 2 12 Ga The result obtained by PN Shukla et a/ by cosmogenic element is 4 7 Ga 
and they are found to be same order of magnitude 
Keywords Meteorite, Dergaon 
PACS No. 96 50 
1. Introduction 
The Dergaon meteorite was collected from a sugarcane field near Ahajati bil, around 20 
km south-west of Dergaon of Golaghat District, Assam [92°52E- 26°41,50"N]. The fall was 
initially sighted on 02.03.2001 at around16.40 local time. Preliminary minerologic and 
petrographic studies suggested that the meteorite belongs to the H5 Group chondnte with 
a unique K composition (Figure 1). 
In this paper we present the probable age of the meteorite by means of radioisotopes 
present in the meteorite and brief outline of nucleocosmochronology [1-3] of Dergaon 
meteorite. 
2. Calculation 
In chronological models for nucleosynthesis [4], the number of NA of nuclei of atomic 
mass A in the interstellar medium vary as a continuous function of time over the 
nucleosynthesis prior to the formation of the solar system from / = 0 to t = 4 
Corresponding Author 
© 2 0 0 8 IACS 
674 P Dutta, K Duorah and H L Duorah 
Thus 
dN A _ 
dt = *A(t) 
N, Q<t<A (D 
where 
kA(t)-> Production function 
£A Mean radioactive life time for the nucleus. 
1.4 
1.2 
Fa Ni Ir Ot Au Cr Co Al Ca Mg Mn As Zn Se Sc Na K La Sm Eu Yb 
Elements 
Figure 1. Chemical composition of Dergaon meteorite. 
Here the production function is applicable to a given process of nucleosynthesis. The 
number NA is the number which is produced in this process and which survives decay 
from t = 0, when process started in galaxy, to t = A, when process contributed to the 
solar system material. The formation of the solar system marked the end of nucleosynthesis 
contribution to the solar system. Again, between the nucleosynthesis event contributing 
to the solar system and the meteorite formation time there is a time interval, which is 
represented by a standard Gambit. Now by the time of formation of the parent body of 
meteorite is meant the time when meteorite material becomes a closed system with no 
further changes in the nuclear abundances except for those due to radioactive decay and 
no separation of radioactive nuclei from their decay product. Therefore, if we represent the 
age of the solar system by As and age of the meteorite by AM, we have 
AS = AM+S. (2) 
The schematic diagram for this is represented in Figure 2. 
So to predict the age of the solar system, the meteorite age has to be evaluated. 
Nucleocosmochronology of Dergaon meteorite 675 
Now the value of standard gambit is 8 =0 17 x 109 yrs\ Therefore, in finding out the 
age of the solar system, the age of the meteorite plays a vital role 
EXPONENTIAL^ 
GALACTIC > exp (-t/TR) 
8YNTHE8IS J 
SOLAR 8YSTEM 8PIKE 
(SUPERNOVA?) 
GALAXY FORMATION 
SOLAR SYSTEM FORMATION I 
PRE8ENT-
*— METEORITES 
Figure 2 Chronological model of nucleosynthesis showing exponential synthesis [4] 
To find the age of the meteorite we use radiometric or radioisotope dating method 
For a radiogenic isotope the equation which represents radioactive decay is 
D - D + D (ex* -11 
'"'now ^original T ^ now \ c '/ 
D —> Daughter Nuclei 
P -> Parent Nuclei 
f = 1/A ln[(D, now original ) /P + 1] 
For above naturally occurring isotopes could be used In Dergaon meteorite radioisotopes 
present in it during time of fall are recorded in Table 1 
40 
4% 
19 
Ar 
Figure 3. Principal decay mode of 40K [1] 
676 P Dutta, K Duorah and H L Duorah 
Table 1. Radioisotopes at the time of fall (March 2, 2001) of Dergaon meteorite [3] 
Isotope 
48y 
51Cr 
7Be 
^Co 
afco 
46Sc 
57Co 
MMn 
^Na 
«fco 
26AI 
40K 
Half-life 
16 d 
27 7 d 
53 3 d 
70 78 d 
78 8 d 
83 9 d 
271 35 d 
3122 d 
2 6 Y 
5 27 Y 
7 3 x 105Y 
1 28 x 109Y 
(K=340 ppm)a 
Y-energy 
(keV) 
983 5 
1311 6 
320 07 
477 56 
810 75 
846 75 
889 26 
122 07 
834 8 
1274 54 
1173 23 
1332 51 
1808 65 
1460 75 
Koilaghat fragment 
14 kg 
cpm 
0 15±0 02 
011±0 01 
0 11±0 01 
0 11±0 01 
0 26±0 01 
1 59±0 01 
1 02±0 01 
0 02 
0 003 
0 52±0 004 
0 96±0 01 
dpm/kg 
56 1±7 5 
5 3±0 5 
5 5±0 5 
5 5±0 5 
9 1±0 4 
76 5±0 9 
71 6±1 0 
<14 
<0 2 
52 2±0 7 
Balidua fragment 
1 8 kg 
cpm 
0 37±0 03 
0 29±0 02 
0 18±0 03 
0 17±0 01 
0 15±0 01 
0 14±0 01 
0 15±0 01 
0 28±0 02 
1 92±0 02 
1 39±0 01 
0 02±0 01 
0 74±0 01 
1 30±0 01 
dpm/kg 
14 4±1 2 
15 4±1 1 
46±7 7 
47±2 8 
5 3±0 4 
5 1±0 4 
5 5±0 4 
7 2±0 5 
68 2±0 9 
72 0±0 8 
<1 0 
54 9±0 9 
Balidua box 55 5 g 
cpm dmp/kg 
0 24±0 01 84 7±3 5 
0 11±0 01 56 6±5 1 
0 06±0 003 44 2±2 2 
0 15±0 006 
The occurrence of 40K can be used for dating purpose 
In the case of potassium the principal kind of decay is to 40Ca and 40Ar However, 
decay to 40Ca is not useful because 40Ca is the most common isotope and the amount 
produced radiogenically is not detectable Decay scheme for 40K is shown in Figure 3 
Since two separate decay types are possible, the decay equation is somewhat 
complicated. 
Let A be the total decay constant. AAr be the decay constant for K Ar and ACa 
be the decay constant for K -» Ca. Then total decay 
dTK 
dt (*Ar+*Ca)*°K = ^K 
Now the decay equation for K-> Ar leads to 
Arnow = Aronginai + [A.Ar / A ) Know ye - 1 j 
As original Ar^nal would not survive formation except under very unusual 
circumstances, we put 
r4U , = o 
original u 
Nucleocosmochronology of Dergaon meteorite 677 
t = V*\n[Ar™w/K*n°owmAr)^] 
where decay constants A, kAn X0a are given in Table 2. 
Table 2. Decay constants A, A^r, ^ [2] 
4.962 X 10-10 yrs'' 5 543 X 10"10 yrs 1 0 581 X 10 10 yrs 1 
The relative abundances of K40 and Ar40 are reported in Table 3 
Table 3. Relative abundances of 40K and 40Ar 
Target Isotope % Abundance 
36Ar 0 337% 
38Ar 0 063% 
4<>Ar 99 6% 
39K 99 10% 
<0K 0 0119% 
«'K 6 88% 
Therefore, from Tables 2 and 3 we can find out the age of the Dergaon meteorite 
3. Result 
Thus the result obtained for the age of the meteorite by using radiometric dating and the 
result obtained by P.N. Shukla et al [3] by cosmogenic element are 
Calculated Value 2.12 Ga 
P.N. Shukla 4.7 Ga 
4. Conclusion 
Age of the Dergaon meteorite gives only the first step for galactic evaluation Future 
measurement and more elaborate studies will be required for the study of s-process, r-
process and ^process in the element formation of the Dergaon meteorite and thereby a 
better understanding of the nuclear cosmochronology of Dergaon meteorite. 
Acknowledgment 
We gratefully acknowledge the U.G.C., New Delhi for financial assistance [MRP No. F-5-
29/2005-06 (MRP/NERO)] 1548. 
678 P Dutta, K Duorah and H L Duorah 
Reference 
[1] E M Durance Radioactivity in Geology, Pnnciples and Application (U K Ellis Horwood Ltd ) p2PP 
(1986) 
[2] Overmann and Clark Radioisotopes Techniques (USA Mc Graw Hill Book Company Inc) p4V 
(1960) 
[3] P N Shukla et al, Meteontics and Planetary Science 40 (4) 633 (2005) 
[4] W A Fowler Cosmology, Fusion and Other matter (ed) Frederick Reines (George Gamow Memorid 
Volume) (U K Adam Hilger Ltd) p71, p78 (1972) 


English

Nucleocosmochronology of Dergaon Meteorite

Devi, R

Kalita, P K

Purkayastha, P

Sarma, B K

Indian J. Pirn 82 (6), 707-713 (2008) 
Synthesis and optica! characterization of CdS 
nanocomposites 
R Devi1*, P K Kahta2, P Purkayastha-2 and B K Sarma1 
department of Physics Gduhati UnivcisrtvGuw.ihati 781 014 Assam Indi 
^Department of Physics Guwahati Colieqc Guwahati 781 021 Assam Indi. la 
£ mail kuhkhdk" yahoo com 
Abstract Nanocrystalline films are deposited in plastic substrates and particles in powder form are preparod 
by precipitation method from the same colloidal solution The size and distribution of the crystallites are controlled 
by varying the temperature of the bath solution from 28(,C to 90°C The crystallite sizes are determined from X 
ray diffraction and are found to be around 7 nm in films and 15 - 10 nm in powder The band gaps are determined 
from the UV absorption spectra and are found to be within the range from 2 48 2 75eV in films and 2 48 2 64 
eV in powder Photolummescence measurements shows enhancement of PL intensity for films at higher 
temperatures whereas excitonic emission at 376 nm and red shift around 603 nm is observed for precipitates 
Keywords Chunual nuihnd nanomaiuial U\ spittt i phololumniLsiAiuc uiugy hand gap 
PACS Nos. 81 15 - z , 68 55 - a 
1. Introduction 
Semiconductor nanocomposites like all nanomatenals are found to exhibit properties 
different from those of the same materials in bulk form[1,2] Evidences of variations of the 
properties with sizes of the particles open up new theoretical, experimental and technological 
interests Of the 11-VI semiconductors CdS have received wide attention because of its 
immense application potentials in optoelectronic nanodevices[3,4] CdS is a typical direct 
band gap semiconductor having band gap of 2 42 eV for bulk material which increases 
when crystallite size decreases Sizes of the CdS clusters depend strongly upon their 
preparation conditions and methods[5,6,7] The simple way of synthesizing CdS 
nanoclusters is through an arrested precipitation reaction of Cd2+ and S2 in an aqueous 
solution with the presence of a stabilizing agent, such as polymers[8], zeolites[9], or 
porous glass[10].Out of several methods for deposition of nanocomposites, chemical bath 
Corresponding Author 
©2008IACS 
708 R Devi, P K Kalita, P Purkayastha and B K Sarma 
deposition (CBD) technique using polymer matrix is relatively simple, cost effective and 
suitable for deposition of large area films. 
2. Experimental details 
In the present work systematic analysis on the growth of the film by CBD technique as 
well as on homogeneous precipitation of clusters taking place simultaneously in the solution 
are carried out.The deposition was carried out in a mixture of matrix solution and thiourea 
The matrix solution was prepared by adding cadmium sulphate to an aqueous solution 
(2%) of polyvinyl alchohol (PVA) with constant stirring at constant temperature (70°C) 
maintained for 90 minutes. Different solutions were prepared with the same concentration 
of cadmium sulphate (1M) The pH of the solutions were maintained at around 11, by 
slowly adding NH4OH solution. Then the equimolar solutions of thiourea were added to 
the mixture solutions kept at different temperatures (28°C & 90°C). Deposition of CdS 
thin film at higher temperature facilitates comparatively faster growth of the film Plastic 
substrates were introduced vertically into the solution with the help of substrate holder 
The substrates were kept in the solution for 20 hrs at room temperature and 20mins at 
elevated temperatures for deposition of films. After deposition the substrates were taken 
out and thoroughly washed and rinsed with doubly distilled water and dried in air The CdS 
precipitate that formed in the bath was filtered out and after thoroughly washing by distilled 
water was allowed to dry for two days in a desiccator containing silica gel at room 
temperature. 
2 1 Characterization of CdS thin films : 
All the measurements were done at room temperature. Grain sizes of the films and 
precipitates were measured by X-ray diffractometer (Philips X-pert Pro diffractometer (PW 
1830)) with CuKa radiation in the 20 range of 2 0 ° - 35° Surface morphological study 
were done using the Scanning Electron Microscope (SEM) (LEO 1430 VP) operating 
with an accelerating voltage 20 kV. Optical absorption spectra at 300 K were obtained 
using a UV visible spectrophotometer (VARIAN CARY 300 Scan) in the wave length range 
300 nm to 700 nm. Photoluminescence (PL) spectra were obtained with a luminescence 
spectrometer(Thermo Spectronic(Ammco Bowman Series 2)) operating at detector voltage 
700 volt with an excitation light wavelength of 325 nm. 
3. Results and discussion 
3.1. X-ray diffraction : 
The X-ray diffractogram of the CdS nanocrystalline films and precipitates show broadened 
diffraction profiles (Figure 1(a) and (b)). It is observed that XRD patterns show a preferred 
orientation along (002) plane.The observed XRD pattern exhibits hexagonal phase as 
confirms from JCPDS data 08-006.The crystallite sizes of the nanocrystallites are estimated 
using Scherrer formula 
D = KA//}20 cos 6 (D 
Synthesis and optical characterization of CdS nanocomposites 709 
where K is a constant taken to be 0.94, A the wave length of X-ray used ( / =1.54A°) 
and p20 the full width at half maximum of (002) peak of XRD pattern, Bragg angle 20 
is around 26.5°. The crystallite sizes were found to be about 7 nm for films, and 15 -10 
XRD for Powder XRD for Films 
1 * 28c 
2 = 90c 
Figure 1 (a). XRD patterns \or films deposited 
at temperatures 28°C and 90°C. 
Figure 1 (b). XRD patterns for precipitates 
deposited at temperatures 28°C and 90°C 
nm for precipitates and are shown in Table 1. It is observed that crystallite size decreases 
with the increase in temperature of the solutions. 
Table 1. Crystallite sizes and band gaps for CdS nanocrystalline films and precipitates 
having different temperatures 
SI.No. 
Film 1 
Film 2 
Powder 
Powder 
1 
2 
Temp of the 
SOlnS (°C) 
28 
90 
28 
90 
Grain Size (nm) 
From XRD 
7 
7 
15 
10 
Gram Size (nm) 
From SEM 
47-54 
32-37 
82-94 
59-74 
Banc 
From 
I Gap (eV) 
UV spectra 
2 48 
2 75 
2 48 
2 64 
3.2. SEM analysis: 
Figure 2(a) and (b) show the surface morphology of the CdS nanocomposites deposited 
at two different temperatures observed by SEM. From the Figure, we clearly observe the 
small nanosized grains engaged in a fibrous-like structure, which clearly indicates the 
nanocrystalline nature along with some amorphous phase of CdS thin films. From these 
images, it can be seen that the grain sizes are not uniform and found to be about 32 -
94 nm and shown in Table 1. 
3.3. Absorption studies: 
The UV absorption spectra of the CdS thin films and of the precipitates obtained from 
different solution temperatures (28°C and 90°C) are taken at room temperature and shown 
710 R Devi, P K Kahta, P Purkayastha and B K Sarma 
Figure 2(a). SEM pictures for films at temp 28°C and 90°C 
Figure 2(b). SEM pictures for precipitates at temp 28°C and 90°C 
in Figure 3(a) and (b) From the spectrographs the absorption edge of the samples are 
found to occur in the range 340-490 nm. 
Absorption spectrum shows a clear shift of the absorption edge to the lower wavelength 
side over bulk value at ~ 515 nm. This blue shift of the absorption edge indicates decrease 
of the crystallite sizes of the samples. The absorption coefficient is given by 
28c =1 
350 450 550 650 
Wavelength In nm 
Figure 3(a). UV spectra for films at temp 
28°C & 90°C 
Figure 3(b). UV spectra for precipitates at temp 
28°C & 90°C 
Synthesis and optical characterization of CdS nanocomposites 711 
cc = c(hv-Eg)V2/hv, (2) 
where cc is the absorption coefficient, c is a constant, to the photon energy and E the 
band gap. A graph between hv vs (atof is plotted and shown in Figure 4(a) and (b). 
The extrapolation of straight line to (atof = 0 axis gives the value of the energy band 
gap of the materials and the band gaps are found to be within 2.48 - 2.75 eV. The band 
gap increases with the decrease of crystallite sizes. 
3 5 1 
3 -
2 5 • 
i . 2 " 
3 1 5 -
1 • 
0 5 -
0 -
• 28c 
• 90c 
m 
hv Vs (cxhv)2 curves 
y 
s y, y y 
s s 
^ ** 
m,t»0U**f 
40 
35 -
30 -
25 -
L 
£ 20 -
15 -
10 -
5 -
0 -
• 
A 
hv vs (uhv)*' 
_ 
90c ./' ^ ' 
y / / 
* A 
| ^ 1 | 1 1 1 1 
2 0 2 2 2 4 2 6 2 8 3 0 3 2 3 4 
hv in eV 
Figure 4(a) Band gap determination for films 
at temp. 28°C & 90°C. 
2 0 2 2 2 4 2 6 2 8 3 0 3 2 3 4 
hv in eV 
Figure 4(b). Band gap determination for 
precipitates at temp 28°C & 90°C 
3.4. PL spectra: 
It has been reported that, in case of CdS nanoparticles (NP's) embedded in polymers, 
the peak position of the surface defect PL emission of CdS NP's is weakly related to the 
size of the NP's[11]. However, PL spectra is more dependent on the surface states of the 
nanoparticles. 
A room temperature PL spectra of two representative films deposited at solution 
temperatures 28°C and 90°C are shown in figure 5. At 28°C, the maximum PL peak at 
520 nm is due to the band-to-band transition. However, at 90°C, the PL emission peak is 
more intense and shifted to the lower wavelength side at 436 nm. The other less intense 
broad peaks at 658 nm and 696 nm found in the long wavelength region is expected due 
to transitions at surface defect states [11,12,13,14]. Moreover, the intensities of 
both the PL peaks are found to increase when deposition temperature of the films are 
increased. 
In case of precipitates, the less intense PL peak at 376 nm may be due to excitonic 
emission because of quantum confinement [15]. The excitonic energy is calculated to be 
3.3 eV. The other intense sharp peak at 603 nm, clearly shows red shift because of the 
surface states of CdS nanoparticles. The defect level calculated to be 2.05 eV is a deep 
state preferably arises from sulphur vacancies. Further studies on this precipitates (powder 
samples) are in progress. 
712 R Devi, P K Kalita, P Purkayastha and B K Sarma 
436 nm 603 nm 
350 400 450 500 550 600 650 700 750 800 
Wavelength (nm) 
Figure 5(a). Photoluminescense spectra for films 
at temp 28°C and 90°C. 
Wavelength (nm) 
Figure 5(b). Photoluminescense spectra for 
precipitates at temp. 28°C and 90°C 
4. Conclusion 
Thin films as well as precipitates of CdS prepared by CBD technique in PVA matrix are 
found to be nanocrystalline. The crystallite sizes are found to be within 7 - 1 5 nm. The 
UV absorption of films at higher temperatures clearly shows an increase in band gap 
which supports the formation of nanocrystallites. It, therefore, shows that the films prepared 
at elevated temperatures of the solution exhibited strong quantum confinement effect as 
the optical band gap increases significantly, from 2.48 - 2.75 eV compared to bulk value 
2.42 eV. Enhancement of PL intensity is also observed for the films prepared at higher 
solution temperatures. In case of precipitates, the PL emission spectra are dominated 
by surface defect level rather than band to band transitions. 
Acknowledgment 
One of the authors, R.Devi thanks UGC for providing a teacher fellowship for the period 
when the work was being done. 
References 
[1] H Tang, M Yan, H Zhang, M Xia and D Yang Mater. Letts. 59 1024 (2005) 
[2] R He, X Qian, J Yin, L Bian, H Xi and Z Zhu Mater. Letts. 57 1351 (2003) 
[3] Lee Jae-Hyeong Thin Solid Films 431 344 (2003) 
[4] S S Dhumure and C D Lokhande Indian J. Pure & Appl. Phys. 31 512 (1993) 
[5] B Liu, G Q Xu, L M Gan and C H Chew J. Appl. Phys. 89 No. 2 1059 (2001) 
[6] R Devi, P Purakayastha, P K Kalita and B K Sarma Bull. Mater. Sci. 30 123 (2007) 
[7] R Devi, P Purakayastha, P K Kalita, R Sarma, H L Das and B K Sarma Indian J. Pure & Appl. Phys 
45 624 (2007) 
[8J X K Zhao, S Barai, R Rolandi and J H Fendier J. Am. Chem. Soc. 110 1012 (1988) 
[9] N Herron, Y Wang, M M Eddy, G D Stucky, D Cox, K Moiler and T Bein J. Am Chem. Soc. 111 350 
(1989) 
Synthesis and optical characterization of CdS nanocomposites 713 
[10] K M Choi and K J Shea J Phys Chem 98 3207 (1994) 
[11] Y Lei, W K Chim, H P Sun and G Wilde AppI Phys Lett 86 103106 (2005) 
[12] B Bhattacharjee, D Ganguli and S Chaudhuri J Nanopart Res. 4 225 (2002) 
[13] Z Q Wang, J F Gong, J H Duan, H B Huang, S G Yang, X N Zhao, R Zhang and Y W Du AppI 
Phys. Lett. 89 033102 (2006) 
[14] S N Behera, S N Sahu and K K Nanda Indian J Phys 74A(2) 81 (2000) 
[15] P Ayyub, P Vasa, P Taneja, R Banerjee and B P Singh J AppI Phys 97 104310 (2005) 


Synthesis and Optical Characterization of CdS Nanocomposites

Bhunia, S

Biswas, S

Sarkar, D

Sarkar, P P

flfepid Communication 
Indian J. Phys. 82 (7) 829-832 (2008) 
# 
Experimental investigation on single layer single-feed 
dual frequency (dual band) reduced sized slotted square 
microstrip patch antenna 
S Bhunia1, S Biswas2, D Sarkar2 and P P Sarkar2* 
1Academy of Technology, Hooghly-712 121, West Bengal, India 
2USIC, University of Kalyani, Kalyani, Nadia-741 235, West Bengal, India 
E-mail : parthabe91@yahoo.co.in 
Received 14 August 2007, accepted 13 May 2008 
Abstract : A novel, compact, single probe-feed square microstrip patch antenna for operation in dual frequency 
can be achieved by cutting a circular slot having an inner square patch at its centre.From the experimental results 
obtained, the antenna size using the proposed design method can be reduced by about 70% compared to what is 
achieved in conventional design method using a simple square patch without the slot. This paper focuses about 
the typical results obtained experimentally. 
Keywords : Dual frequency, dual band microstrip antenna. 
PACSNo. : 84.40.Ba 
1. Introduction 
In the designing of global positioning system and voteless communication, system 
miniaturization of the antenna has a vital role. Due|to the lightness of microstrip 
antennas, they are well suited for systems to be moused on airborne platforms, like 
synthetic-aperture radar (SAR). The broadening of tota^bandwidth can be achieved by 
using dual frequency patch antenna. Dual frequency antennas exhibit a dual resonant 
behavior in a single radiating structure. If any system requires two resonant frequencies, 
too far apart, dual frequency antenna with higher frequency ratio can be used instead 
of two different.antenna arrays to reduce the area and weight. Different techniques 
have been reported to reduce the patch antenna size, such as a square-ring patch fed 
by a microstrip line, the use of cross and bend slots embedded in the radiating patch 
[1-3] and the use of a slot in the ground plane [4}. Another duai frequency antenna 
•Corresponding Author • 2 0 0 8 , A C S 
830 S Bhunia, S Biswas, D Sarkarand P P Sarkar 
with square slot or rectangular slot loading have been reported in Refs. [5,6]. A 
compact dual-frequency microstrip antenna has been proposed in Ref. [7], which uses 
the rectangular microstrip patch loaded with one shorting pin. Characteristics of dual 
frequency compact rectangular microstrip patch antenna with a number of shorting pins 
have also been studied in Ref. [8]. A size reduction of the microstrip patch up to 51%, 
operating in dual-polarization mode by cutting symmetric pattern of cross slots from the 
square probe-fed patch has been reported in Ref. [9]. 
In this paper, we propose a single-feed antenna design by cutting a circular slot 
having an inner square patch at its centre. Results show that the proposed antenna 
is about 70% smaller compared to a traditional square patch antenna operating at the 
same frequency and we get the dual frequency operation in two different bands i.e. 
S and C bands having frequency ratio 
2. Antenna design 
The configuration of the compact-dual frequency antenna is shown in Figure 1. The 
antenna consists of a square microstrip patch of side L = 26 mm with a circular slot 
of diameter D « 20 mm having an inner square patch of side length W = 10 mm 
supported on a grounded dielectric sheet of thickness h = 1.5875 mm and dielectric 
constant er = 2.4. The probe feed (radius rp = 0.5 mm) is placed at the center of the 
square patch. Due to the additional slot perturbation for the horizontal patch surface 
current path as compared to the reference antenna without slot, surface current paths 
of the two resonant modes can be lengthened, which lowers the corresponding 
resonant frequencies. 
Ground plana 
Figure 1. Geometry of square patch antenna with a slot. 
Experimental Investigation on single layer single-feed dual frequency (dual band) etc. 831 
3. Experimental results 
Figure 2 shows the typical results of the measured return loss. The first two resonant 
frequencies are 2009 MHz and 6112.5 MHz. The corresponding return losses are 
-10.7 dB and -15.8 dB. The 10 dB bandwidth of the first resonant frequency is about 
44 MHz, which is 2.19% of the resonant frequency. The 10 dB bandwidth of the 
second resonant frequency is about 150 MHz, which is 2.454% of the resonant 
frequency. The reference square patch antenna without slot resonating at 2009 MHz 
has the dimension L = 47.23 mm. However, the antenna proposed in this work has 
the dimension of L = 26 mm only. Hence, an antenna size reduction of about 69.69% 
can be easily achieved. Chen et al. has reported [5] 17% size reduction by cutting a 
square slot inside the rectangular patch. The 10 dB bandwidth of about 1.8% and of 
2% have been reported for the two resonant frequencies 1932 MHz and 2475 MHz. 
0.00E+00 
-2.00E+00 
-4.00E+00 
-6.00E+00 
-8.00E+00 
-1.00E+01 
-1.20E+01 
-1.40E+01 
-1.60E+01 
-1.80E+01 
Frequency (Ghz) — > 
Figure 2. Return loss against frequency. 
Figure 3 shows the radiation pattern of the proposed microstrip antenna in which 
the normalized amplitude (in dB) and radiation angle are plotted along Y axis and X 
axis, respectively. It is seen that the radiation pattern In H plane is better at higher 
frequency. The half-power beam width is about 100° and 120° for the 1st and 2nd 
resonant frequencies, respectively. 
-3SJ 
For the 1* 
resonant 
frequency 
Figure 3. Radiation pattern. 
832 S Blum, S Biswas, D Sartor and PP Sartor 
4. Conclusion 
In our designed slotted square microstrip patch antenna, we have two resonant 
frequencies. Considering 10 dB bandwidth, we have 2.19% and 2.45% bandwidth of 
the two resonant frequencies that are better than the experimental results reported in 
Refs. [5,9]. At the same time, we have achieved about 70% size reduction. The two 
frequencies in two different bands i.e. S and C bands are well separated having the 
frequency ratio -3.04. The above results are encouraging. The proposed antenna may 
be used in synthetic-aperture radar (SAR) system. 
References 
[1] C Y Huang, J Y Wu and K L Wong IEEE Trans. Antennas Propag. 47 605 (1999) 
(2] H Iwasaki IEEE Trans. Antennas Propag. 441399 (1996) 
[3] W S Chen, C K Wu and K L Wong Electron. Lett. 34 1278 (1998) 
[4] J S Row and C Y Ai Electron Lett 401093 (2004) 
[5] W S Chen Electron Lett. 34 231 (1998) 
[6] S C Gao and J Li Progr. Electromagn. Res. PIER 23 59 (1999) 
[7] K L Wong and W S Chen Electron. Lett. 33 646 (1997) 
[8] S C Gao and L W Li IEEE Transaction on Vehicular Technology 51 8 (2002) 
[9] K Gosalia and G Lazzi IEEE Trans. Antenna Prop. 51 2182 (2003) 


Experimental Investigation on Single Layer Single-Feed Dual Frequency (Dual Band) Reduced Sized Slotted Square Microstrip Patch Antenna

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Dielectric Study of Particulate Material in e.m. Field at Microwave Frequencies

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Notes for Contributors

Mihaela, Osaci

Indian J. Phys. 82(12) 1671-1679(2008) 
m 
Determination of the effective magnetic anisotropy constant 
of ferrite nanoparticles dispersed in organic matrix 
Osaci Mihaela 
Electrical Engineering and Industrial IT1 Department, Faculty of Engineering Hunedoara, 
"Pohtehnica Timisoara" University, 5 Revolutiei Street, Zip code 331128, Romania 
E-mail osaci mihdela(ctffih upt ro 
Received 22 April 2008, accepted 25 August 2008 
Abstract : With increasing interest in realising new magnetic materials, the magnetic behaviour of the 
nanoparticle disperse systems became an important problem both from the experimental point of view and 
from the theoretical one The researches performed in the last period show that, by controlling the size 
distribution, the effective anisotropy constant and the nanoparticle concentration, the nanoparticle disperse 
systems can be used for realising magnetic materials with special properties This paper presents a modality 
to determine the effective anisotropy constant of the mixed ferrite nanoparticle of NiZn, dispersed in the solid 
organic dielectric matrix - Nestrapol 450 In this respect, there are realised samples with low nanoparticle 
concentration, which are studied in dynamic magnetic fields through the 0-metnc method, using a coaxial 
transmission line in short-circuit So, it can determine the dependence of the complex magnetic permeability 
components, the tangent of the magnetic loss angles and material quality factor, on the frequency, and then 
we can calculate the medium N6el relaxation time and the effective anisotropy constant of the nanoparticles 
Keywords : Fine-particle systems, magnetic properties, nanoparticles, composite materials 
PACS Nos.: 78 66 Vs, 74 25 Gz, 61 46 Df, 72 80 Tm 
1. Introduction 
For a given substance, the effective magnetic anisotropy constant depends on the 
method of nanoparticle generation. So, for the magnetite nanoparticles, Raiker and 
Shhomis [1] indicate values of this constant in the range 103-104 J/m3. In the same 
time, Kneller presents [2] values determined by many authors, refer to the effective 
magnetic anisotropy constant of massive samples, at room temperature. They set in 
the range (7.3-14)-103 J/m3. For the mixed fernte nanoparticles of ferro-fluids types 
Mn04Zn06Fe2O4 and Mn04Zn06Fe2O4, the effective magnetic anisotropy constants have 
been determined [3] (values found : 1.9-103 J/m3 and 1.3 103 J/m3). In case of mixed 
© 2008 IACS 
1672 OsaciMihaela 
ferrites, Dillon [4] indicates the value 7.2-103 J /m 3 for the anisotropy constant of a 
sintered ferrite sample of NiZn. 
In the magnetisation process of a nanoparticle system dispersed into a solid 
matrix, the magnetic moment rotation dependents on the nanoparticle, this one 
remaining fixed. Owing to this mechanism, there appears a N6el relaxation moment [5] 
associated with the magnetic moment rotation, inside the nanoparticle, the corresponding 
relaxation time being correlated with the material properties of the particles. In case of 
a low nanoparticle concentration, so that we can neglect the dipole magnetic 
interactions among the nanoparticles, the expression of the Neel relaxation time has 
been established by Brown, in the form [5] : 
{ K V
'
 ( . ) kBT 
where V is the volume of the particle magnetic core. In the relation (1), based on the 
study presented in the paper [2] : 
V4a3 
0N
 ~ y ^ p r * rB., (2) 
KV 
where a =. — - , K = effective magnetic anisotropy constant of the nanoparticles, V = 
KQT 
average volume of the nanoparticle, kB = Boltzmann constant, T = absolute temperature, 
and rBI = relaxation time "inherent Brown", introduced due to the analogy between the 
rotation motion of the magnetic moments, inside the particle, and the Brown rotation 
of the particle : 
r B , = ^ , (3) 
Bl
 kBT 
where rjm is "the internal magnetic viscosity" which depends on the nature of the 
material. Replacing (3) in (2) and taking into account the expression of the non-
dimensional ratio a, it results : 
-
3!hn I. 
~ 2K i 
7r/f=T 
' 0 * - ^ , - ^ - . (4) 
The motion of the magnetic moments in the magnetic field H, versus the crystal axes 
of the particles, is described by the equation Landau-Lifschitz [1] : 
-~~ = - 7 {mxfi0H) - 5jl [mx(#nx/x0H)], (5) 
where a is a non-dimensional damping constant and 7 is a gyromagnetic factor. In a 
constant field, the first term (from right) of the relation (5) represents the free 
Determination of the effective magnetic anisotropy constant offernte nanoparticles etc 1673 
precessional motion of the magnetic moments around the H direction with Larmor 
frequency uL = 7 ^ The second term, which represents a vector directed from the 
magnetic moment direction to the applied field direction, determines the reduction of 
the precession angle The time when the magnetic moments direction overlaps the field 
direction is exactly the Neel relaxation time rN The factor b, - - ~ ~ in the relation 
(5) represents the rotational mobility of the magnetic moments Therefore, for the 
rotational diffusion coefficient of the vector m, according to Einstein's formula [2], we 
have D, = b,kBT = — Taking into account the definition of the diffusion time rB) 
fi0m 
= (2D,)"1 and the relation for the magnetic field of the monodomam particle (m = VMS, 
where Ms is the saturation magnetisation of the solid material which the particle comes 
from), we obtain . 
* " 2pykBT • ( 6 ) 
From (3) and (6), we get the explicit expression for the magnetic viscosity 
i. = f* m 
By introducing (7) in (4), for r0N we obtain the expression 
T -J*-T„a 1/2 (8) 
TQN — TQU \ / 
with 
2oryK 
which represents the relaxation time of the precessional motion in the anisotropy field 
Ha. If, at the moment f = 0, the vector m deviates from the low magnetisation direction 
with an angle 0O, then, under the action of the anisotropy field, the angle between m 
and Ha varies in time, according to the relation . 
0(f ) = 0oexp <10) 
If we introduce (8) in (1). we obtain the Neel relaxation time [5] 
•& nL„«„ (11) 
T W = T O N expa = — - - 2 ° 
1674 OsaciMihaela 
where r0 is given by the relation (9) and a = - — . 
KQT 
The relaxation processes involve dissipative processes that are described by the 
dependence of the imaginary component x " of the complex magnetic susceptibility on 
the field frequency. According to Debye [6], the N6el relaxation time is correlated with 
the angle frequency u;max, where x " is maximum according to the relation : 
^max^ = 1. (12) 
As example, we will realise a sample with low concentration of mix ferrite NiZn. 
Through a O-metric method, using a line with short-circuit transmission as sample, we 
will determine the dependence of the imaginary component x" . complex magnetic 
susceptibility or the imaginary component of the complex magnetic permeability //" on 
the applied field frequency. From the dependence graph / / ' = /(f), we will determine 
the frequency that corresponds to the peak of the curve. We will introduce the value 
of this frequency in the Debye relation (12) to determine the average Neel time for the 
magnetic relaxation and then, from the relation (11), through graphical plotting, we will 
determine the effective average magnetic anisotropy constant of the nanoparticles. 
2. Sample preparation 
The sample is made of nanometric dielectric ferrite powders, having organic nature. The 
nanometric powder is mix ferrite NiZn, Ni0i2Zna8Fe2O4( obtained through atomisation, 
with the average magnetic diameter of 13 nm, having spontaneous magnetisation Ms = 
2.85-105 A/m. The used organic matrix is Nestrapol 450, an unsaturated polyester 
resin in liquid state. During mixing and homogenising the powder-Nestrapol mixture, we 
added a plasticiser - cobalt naphthenate and a hardener - butanox (peroxide of methyl-
ketone), and then the mixture was poured in moulds. The mixture solidified in the 
moulds in few hours, at the room temperature, depending on hardener quantity. We 
obtained a toroid sample, with the length smaller than the length of the coaxial 
transmission line used in the measuring installation. The apparent volumetric fraction 
(the volume occupied by the unpressed powder spread in the sample volume) is 0.7335 
and the real one is 0.3836. 
3. Method for measuring the complex magnetic permeability in a radiofrequency 
field 
Experimental results 
To determinate the components of the complex magnetic permeability, we used a 
O-metric method [7] based on the determination of the complex impedance of the 
sample, z$ = Rs + jXs with the help of the short-circuit transmission coaxial line 
technique. In case the transmission line is not full of material, the method presented 
Determination of the effective magnetic anisotropy constant of ferrite nanoparticles etc. 1675 
in [3] and [8] may be used, applied for fluids. The equivalent circuit of the short-circuit 
transmission coaxial line, discharged on the charge impedance zs is presented in 
Figure 1, and the line model is presented in Figure 2. 
li 
+ 0-
Vi 0 
Zo.Yo 
-Q 
x L 
* kL J 
X=0 
Figure 1. The equivalent circuit of the 
transmission line discharged on the 
charge impedance zs. 
Figure 2. The model of the transmission coaxial line 
in short-circuit, discharged on a toroid sample. 
The feed impedance of the transmission line at the distance x from the charge 
(Figure 1) is given by : 
Zi = ~r 
V, Vs cosh(70x) + z0ls sinh(-y0x) (13) 
// /s cosh(70*) + — sinhb0x) 
That can be written as : 
zs + Zpthj^x) 
z,=z<> Z0 + ZsWloX) 
where zQ is the characteristic impedance of the empty line (with air) with 
*«* ... D IHQ 1 . D 
^ = ^ 1 0 ^ = 
2ir d \e, 2ir 
(14) 
(15) 
where D and d are the outer and, the respective, inner diameter of the transmission 
line, and 70 is the propagation constant that can be written : 
7 o « « + # "* 0 6 ) 
with a -> the attenuation coefficient, /3 = 2TT/A - phase factor and A - wavelength 
in line. In case the losses in line are very low o s 0 and 70 = IP, the eq. (14) 
becomes : 
zs + jZptg(Px) 
'
 0z0 + JzBtg(flx) 
(17) 
1676 OsaciMihaela 
In the methods presented in the papers [3] and [8], the relation used is type (17). 
Thenceforth, we will take into account also the attenuation coefficient from the 
propagation constant. In case of coaxial air line in short-circuit, with the length /, 
zs = 0 and Vs = 0. And, from the relation (14), the feed impedance becomes : 
Z /0 = Z0tf7(7o/). (18) 
From the relation (18), using the expression of the hyperbolic tangent, 
th(lol) = 
e10' + e v 
we obtain the propagation constant for the air line : 
- > f r + % 
(19) 
(20) 
=•(0 
Let's consider the case of a discharge coaxial transmission line, on a sample with the 
length L (Figure 2), where 2b and 7o represent the characteristic impedance and the 
propagation constant for the air line. From the relation (14) we obtain : 
Zpth(70x) (21) Zo - Z^/7(70X) ' 
z-, = R, + / * , . (22) 
The values measured through the Q-metric method, Qu C,, Q2, Q>, for the coaxial line 
partially filled with magnetic material (Figure 2), are used in the relations [3], [8] : 
* , = 
K = 
_L 
2nf 
1 
27rf 
' 1 
C,Q, C 
1 • 
'QQO J 
(23) 
(24) 
For / = 1, without the sample, we obtain Ri0 and Xi0, and for /' = 2, with the sample 
presence, we obtain the components Rip and Xip of the charge seen through the line 
with the length A By gradually introducing the value pairs (R,p, Xip) and (Rl0, Xl0) in 
the relation (9) that takes into account the losses, inspite of the ideal relation (17), we 
obtain the impedance components of the line segment (with magnetic material), 
= «x„ + JXX §' * ; *b R *0 ix. *b (25) 
Then, the real component of the magnetic permeability is / / = — - , the tangent of the 
magnetic losses angle is tgSm 
Rv -R 
—, the imaginary component of the magnetic 
Determination of the effective magnetic anisotropy constant offerrite nanoparticles etc. 1677 
o-permeability is : / *" = (ii' + 1)tg6m and the factor of material quality is - / 6 
Experimental results for our sample are presented in Figure 3. 
x 10"= 
tgt>m 
2.5 
2 
1.5 
1 
0.5 
L.J l°.J 
.' o : : 
L Q'Q. 
1.6 
i.4<k-©-0->-Qji>-Q-0-i' 
1 2 
• l u i 
3.5 
3 
2.5 
2 
1.5 2 2.5 3 3 5 
t(H2) 
x icr3 x 107 
-0-. 
o ; 
O <K 
15 2 2.5 3 3 5 
f(Hz) 
x 107 
1 5 0 0 . 5 
1000 
500 
9
 0 
"1.5 2 2.5 3 3.5 
f(Hz) 
x 107 
"1.5 2 2.5 3 3 5 
f(Hz) 
x 107 
Figure 3. The tangent of the losses angle, the complex relative components of the magnetic permeability and the 
quality factor of the material are plotted against the frequency - for our sample. 
Theoretically (Debye theory), it was shown that at the frequency when x" is 
maximum, the condition : xm" = Xm is effective, where \ m ' represents the value of %' 
at the same frequency. But, after measurements, it was seen that / i m " < fim\ i.e. \m" 
<Xm> This kind of deviation can be explained by the fact that only some particles of 
the magneto-dielectric material have a super paramagnetic behaviour. In Figure 3, it can 
be seen that the maximum imaginary component of the complex magnetic permeability 
is obtained at an average frequency of 34 MHz that corresponds, according to Debye 
relation, at the N6el relaxation time rN = 4.68 ns. 
In order to determine the anisotropy effective constant of the sample nanoparticle, 
the N6el relaxation time (11) should be written [having in view also the relation (9)], as 
follows : 
a exp(b-K) 
= 1, (26) 
where a = ^ M ^ k s T and b = — are constants that can be calculated taking into 
AocysV KB' 
1678 OsaciMihaela 
account the value of the giromagnetic factor 7 = 2.41-105s 1A~1m and the damping 
constant a = 0.02 (for most ferromagnetic materials, a is around 10~2). The relation 
(26) is a transcendental equation in the unknown K, whose solution can be graphically 
determined. Let f, be the numerator of the relation (26) and f2 the denominator of the 
relation (26). At the room temperature, the graphical representation of the functions f, 
and f2 is presented in Figure 4. The solution (the value of K) is the value where the 
two curves intercross (i.e. K = 6300 J/m3). 
1000 2000 3000 4000 5000 6000 7000 8000 
Effective magnetic anisotropy constant (J/mc) 
Figure 4. The graphical determination of the effective magnetic anisotropy constant of the mixed NiZn fernte 
nanoparticles dispersed in solid organic dielectric matrix. 
If we consider the particles to be spherical, identical and arranged into a cube 
tangent to nanoparticles, the maximum volumetric real fraction of nanoparticles, in case 
the powder is not pressed, is fmax = 0.523. According to Garcia relation [9], the 
maximum volumetric real fraction of nanoparticles, in case the powder is not pressed, 
8KV 
is fm 0.32- 2 =0 .523 , where ^0 is the vacuum magnetic permeability. From 
VQMS 
this relation, we obtain a limit for K = 6637 J/m3. It can be seen that there is a good 
correspondence with the value determined through the graphical method. The difference, 
between this value and the graphically obtained value, can be explained by the fact 
that the dispersed nanoparticles in Nestrapol 450 are not perfectly spherical. 
4. Conclusions 
The paper presents an experimental study of a composite material, in dynamic 
radiofrequency field, based on mixed NiZn ferrite nanoparticles and, in the same time, 
a method to determine the effective magnetic anisotropy constant of the nanoparticles 
dispersed in an organic dielectric solid matrix. The method takes into account the fact 
Determination of the effective magnetic anisotropy constant offemte nanopartictes etc 1679 
that r0N (from the Neel relaxation time relation) depends on K [relation (9)] and it is 
not considered a constant with the value of 1(T9 seconds, inspite of the claims in 
literature. 
The scientific and technological importance of the dispersed magnetic systems 
of nanometric particles is justified by the possibility of realising advanced magnetic 
materials [10-16], from natural nanostructures to artificial nanostructures : ferro-fluids, 
medium of high density magnetic recording, magnetic sensors, hard and soft magneto-
dielectric electro-technical materials, at usual and high frequencies .. 
In all these cases, the special magnetic properties of the materials can be 
obtained through an adequate check of the effective magnetic anisotropy constant and 
the distribution of nanoparticle dimensions and concentration [17] 
References 
[1] Y L Raikher and M I Shhomis Adv Chem Phys 87 ch 8 (1994) 
[2] E Kneller Ferromagnetisms (Berlin Springer Verlag) (1962) 
[3] I Malaescu Ferrofluids in Radiofrequency Field (Timi^ oara Publishing House MIRTON) (1998) 
[4] J F Dillon and M E Earl J AppI Phys 30 (1958) 
[5] M F Hansen and S Morup JMMM184 262 (1998) 
[6] P Debye Polar Molecules (New York The Chemical Catalog Company) (1929) 
[7] I Hrianca and I Malaescu J Magn Magn Mater 150 131 (1995) 
[8] P C Fannin, T Relihan§i and S W Charles J AppI Phys 23 2003 (1995) 
[9] J Garcia-Otero, M Porto, J Rivas and A Bunde Physical Review Letters 84 nr 1, 167 (2000) 
[10] A L Babichevchev and G G Krylov Nonlinear Phenomena in Complex System 7 298 (2004) 
[11] F J Himpsel, J E Ortega, G J Mankey and R F Willis Advansedm Physics 47 511 (1998) 
[12] R Skomski J Phys Condens Matter 15 R841 (2003) 
[13] J Fidler and T Schrefl J AppI Phys 33 R135 (2000) 
[14] Z Zhang and K Friednch Composites Science and Technology 63 2029 (2003) 
[15] A B Bortz, M H Kalos and J L Lebowitz J Computational Physics 17 (1975) 
[16] S V Nemkov and T R Ruffini International Symposium in Product Development in Engineering Education, 
Halmstad University, Sweden (1996) 
[17] Osaci Mihaela, Abrudean Cristian and Berdie Adela Acta Physica Polomca A 112 nr 6, 1203 (2007) 


Determination of the Effective Magnetic Anisotropy Constant of Ferrite Nanoparticles Dispersed in Organic Matrix

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