1,721,041 research outputs found
Exchange-spring driven spin-flop transition in DyFe2/YFe2 superlattices
No full textExchange-spring driven spin-flop transition is observed in hysteresis loops of an antiferromagnetic [DyFe2 40 Å/YFe2 160 Å]×20 superlattice at temperatures higher than 100 K, with field along the in-plane easy axis [View the MathML source1¯10]. OOMMF micromagnetic simulation reveals that this transition is derived from the magneto-elastic interaction in DyFe2. Conventional exchange spring behavior is also observable at smaller fields. Simulation shows that it is caused by the simultaneous rotation of the magnetization vectors of both the hard and soft layers towards [010]. Experiment and simulation agree qualitatively with each other
The effect of inter-layer diffusion on magnetic exchange spring behaviour
No full textThe effect of inter-layer diffusion between the magnetically hard and soft layers in magnetic exchange spring systems is examined, using 1D and 2D models. It is shown that diffusion across the hard/soft interfaces leads to an increase in the bending field BB. This increase eventually saturates when the bending field BB and the coercivity BC merge. Moreover, if the increase in the bending field BB is large enough, the nature of the magnetic reversal can be affected. This behaviour is illustrated using a YFe2 dominated YFe2/DyFe2 exchange spring system. In this case the 1D model predicts that inter-layer diffusion can drive a magnetic phase change, from negative to positive coercivity. Discrete 2D model calculations of inter-layer diffusion are also presented and discussed. The latter support the predictions of the 1D model. Finally, while the emphasis is on atomic diffusion, some comments are made concerning interface roughness
Transition metal sublattice magnetization and the anomalous Hall effect in (110)-ErFe2/YFe2 multilayers
No full textBulk magnetometry and anomalous Hall effect measurements are presented and discussed, for rare earth (RE)–transition metal compound superlattices, grown by molecular beam epitaxy. The results are complemented with modeled hysteresis curves. It is found that there is good agreement between the anomalous Hall effect and the calculated Fe magnetization curve. This suggests that the anomalous Hall effect, in the REFe2 intermetallics, is driven predominantly by the magnetization MFe of the transition metal sublattice, and not by the total magnetization M. In addition, it is shown that the anomalous Hall effect in the superlattice (110)-[ErFe2(50 Å)/YFe2(150 Å)]×23 can be used to follow the complicated magnetization reversal processes found at high temperatures
Investigation of magnetization reversal in micron-sized stripes of epitaxial-grown (110) Laves phase DyFe2 films
No full textA large-scale striped array of width 3.4 ?m has been fabricated in 400-nm-thick epitaxial (1 1 0) DyFe2 films with Laves phase structure using a UV direct write system. The magnetic and magneto-optical properties of the sample were characterized by a vibrating sample magnetometer and magneto-optical Kerr magnetometry, respectively. The close easy-axis [?1 1 0] direction, confirmed by VSM, was chosen for patterning. The MO Kerr loops reveal that an additional anisotropy can be induced by the shape of the stripes, which can obviously enhance the coercivity of the close easy-axis [?1 1 0] loop. The magnitude of this additional anisotropy was determined to be 4.2 × 105 erg/cm3, which is not sufficient to change the coercivity of the hard-axis loop due to a large intrinsic anisotropy along the hard-axis [0 0 1] direction
Magnetic anisotropy induced by patterning in (110) MBE-grown ternary Laves phase TbDyFe2 films
No full textTernary rare-earth intermetallic Laves phase compounds Tb0.1Dy0.9Fe2, grown by MBE, were characterized by a vibrating sample magnetometer (VSM) and magneto-optical Kerr effect magnetometry (MOKE). Striped arrays with 5 μm-width along an in-plane easy-axis [-1,1,0] direction were defined by a UV direct write system in 400 nm-thick (1 1 0) epitaxial Tb0.1Dy0.9Fe2 films. An additional shape anisotropy of 2.7 × 105 erg/cm3 in magnitude is induced. MOKE measurements reveal pronounced enhancement of the switching field along [-1,1,0] direction. However, the switching field along the hard-axis [0 0 1] direction is unchanged as the intrinsic anisotropy along the [0 0 1] direction is an order of magnitude larger than the induced one. The results demonstrate a possibility of engineering the magnetostriction-to-anisotropy ratio by patterning in epitaxial TbDyFe2 magnetostrictive materials
Engineering coercivity in YFe2 dominated DyFe2/YFe2 superlattice by patterning
No full textSingle crystal 400 nm thick Laves phase [20 Å DyFe2/80 Å YFe2]40 superlattice have been grown by MBE with a (110) growth direction. VSM measurements performed at room temperature with an applied field range of ±1.2×105 Oe, directed along the [001] direction, reveal a unique single-phase-liked ferrimagnetic behavior. A dominant exchange spring behavior is revealed by MOKE measurement along the [–110] direction. Furthermore, for striped arrays patterned along the [001] direction with height-to-width ratio of 0.05, a shape anisotropy of the order of 104 erg/cm3 is induced, resulting into a pronounced change of coercivity due to the comparable magnitude with intrinsic anisotropies. The results demonstrate the feasibility of engineering both single-phase-liked and exchange-spring magnet behavior in Laves phase epitaxial hard/soft superlattices by patterning
Switching the in-plane easy axis by ion implantation in rare earth based magnetic films
No full textAr(+) ions have been implanted into Laves phase epitaxial thin films of YFe(2) and DyFe(2). Magneto-optical Kerr effect and vibrating sample magnetometry experiments show that the easy and hard axes of magnetization in both materials rotate through an in-plane angle of 90°, whilst the strength of the magnetic anisotropy remains unaltered. This is supported by OOMMF computational modelling. Atomic force microscopy confirms that the film roughness is not affected by implanted ions. X-ray diffraction data show that the lattice parameter expands upon ion implantation, corresponding to a release of strain throughout the entire film following implantation with a critical fluence of 10(17)Ar(+) ions cm(-2). The anisotropy of the films is linked to the strain and from these data it is concluded that the source of anisotropy alters from one where magnetoelastic and magnetocrystalline effects compete to one which is governed solely by magnetocrystalline effects. The ability to locally tune the source of magnetic anisotropy without affecting the film surface and without inducing or eliminating anisotropy could be important in the fabrication of high density magnetic data storage media, spintronic devices and magneto-optical materials
Exchange springs in YFe2 dominated DyFe2-YFe2 superlattices
No full textMBE methods have been used to grow single–crystal Laves–phase DyFe2–YFe2 superlattice samples with a (1 1 0) growth direction. In this paper, magnetisation curves for the YFe2 dominated multilayer samples [wDyFe2/4wYFe2]×N, where w=20, 30, 40, and 50 Å, and N=40, 27, 20, and 16, respectively, are presented and discussed. It will be shown that the measured M–H loops are dominated by magnetic exchange springs, which reduce the magnetic coercivity, considerably. In particular, it is possible to engineer samples with a negative coercivity.<br/
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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