1,721,349 research outputs found
Magnetically Frustrated Behavior In Multiferroics R Mn2 O 5 (r=bi, Eu, And Dy): A Raman Scattering Study
Full text linkA temperature dependent Raman scattering study in multiferroic single crystals R Mn2 O5 (R=Bi, Eu, and Dy) was performed. The Raman spectra were measured in the range from 150 to 450 cm-1 involving mostly Mn-O-Mn bending vibrations, complementing our previous work in a higher frequency range involving Mn-O stretching modes. A number of studied phonons present anomalous frequency behavior below a characteristic temperature, T* ∼60-65 K, such as that found for the stretching modes. The sign and magnitude of such anomalous behavior appear to be correlated with the ionic radius of R, being softening for R=Bi and hardening for R=Eu and Dy in the range between TC TN and T*. The anomalous phonon behaviors in both bending and stretching modes are consistent with an interpretation in terms of the spin-phonon coupling in a scenario of strong magnetic correlations. © 2007 American Institute of Physics.1019Wang, J., (2003) Science, 299, p. 1719Hur, N., Park, S., Sharma, P.A., Ahn, J.S., Guha, S., Cheong, S.-W., (2004) Nature (London), 429, p. 392Alonso, J.A., Casais, M.T., Martínez-Lope, M.J., Martínez, J.L., Fernández-Díaz, M.T., (1997) J. Phys.: Condens. Matter, 9, p. 8515Kagomiya, I., Kohn, K., Uchiyama, T., (2002) Ferroelectrics, 280, p. 297Hur, N., Park, S., Sharma, P.A., Guha, S., Cheong, S.-W., (2004) Phys. Rev. Lett., 93, p. 107207Muoz, A., Alonso, J.A., Casais, M.T., Martínez-Lope, M.J., Martínez, J.L., Fernández-Díaz, M.T., (2002) Phys. Rev. B, 65, p. 144423Golovenchits, E.I., Sanina, V.A., Babinskii, A.V., (1997) JETP, 85, p. 156Chapon, L.C., Blake, G.R., Gutmann, M.J., Park, S., Hur, N., Radaelli, P.G., Cheong, S.-W., (2004) Phys. Rev. Lett., 93, p. 177402Blake, G.P., Chapon, L.C., Radaelli, P.G., Park, S., Hur, N., Cheong, S.-W., Rodríguez-Carvajal, J., (2005) Phys. Rev. B, 71, p. 214402Polyakov, V., Plakhty, V., Bonnet, M., Burlet, P., Regnault, L.-P., Gavrilov, S., Zobkalo, I., Smirnov, O., (2001) Physica B, 297, p. 208Higashiyama, D., Miyasaka, S., Kida, N., Arima, T., Tokura, Y., (2004) Phys. Rev. B, 70, p. 174405Ramirez, A.P., (2001) Handbook of Magnetic Materials, 13, pp. 423-520. , Elsevier, New YorkGarcía-Flores, A.F., (2006) Phys. Rev. B, 73, p. 104411Baltensperger, W., Helman, J.S., (1968) Helv. Phys. Acta, 41, p. 668Granado, E., (2001) Phys. Rev. Lett., 86, p. 5385Sushkov, A.B., Tchernyshyov, O., Ratcliff, I.I.W., Cheong, S.-W., Drew, H.D., (2004) Phys. Rev. Lett., 94, p. 13720
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
Phonon Raman Scattering In R1-xaxmno3+δ (r=la,pr; A=ca,sr)
No full textPolarized Raman spectra of single and polycrystalline R1-xAxMnO3 (R=La,Pr; A=Ca,Sr) ceramic samples were studied as a function of temperature. For the rhombohedral LaMnO3.1 and La0.7Sr0.3MnO3, the observed Raman peaks were associated with modes arising from the folding of the Brillouin zone under lattice deformation. For the orthorhombic LaMnO3.0, the Raman spectra are consistent with the Pnma structure and show an anomalous softening of the 494 and 604 cm-1 modes below the antiferromagnetic ordering temperature TN≃140 K. Polycrystalline samples of La0.5Ca0.5MnO3 show a dramatic change of the Raman spectra between 100 and 160 K, which was associated with the increase of the orthorhombic distortion observed by others for T≲240 K. Other R1-xAxMnO3 single crystals, with small orthorhombic distortions, show Raman spectra which are similar to those observed in the rhombohedral samples.58171143511440Jonker, G.M., Van Santen, J.H., (1950) Physica, 16, p. 337. , UtrechtKusters, K.M., Singleton, J., Keen, D.A., McGreevy, R., Hayes, W., (1989) Physica B, 155, p. 362Von Helmolt, R., Wecker, J., Holzapfel, B., Schultz, L., Samwer, K., (1993) Phys. Rev. Lett., 71, p. 2331Hwang, H.Y., Palstra, T.T.M., Cheong, S.-W., Batlogg, B., (1995) Phys. Rev. B, 52, p. 15046Millis, A.J., Littlewood, P.B., Shraiman, B.I., (1995) Phys. Rev. Lett., 74, p. 5144Millis, A.J., (1996) Phys. Rev. B, 53, p. 8434Millis, A.J., Shraiman, B.I., Mueller, R., (1996) Phys. Rev. Lett., 77, p. 175Billinge, S.J.L., DiFrancesco, R.G., Kwei, G.H., Neumeier, J.J., Thompson, J.D., (1996) Phys. Rev. Lett., 77, p. 715Dai, P., Zhang, J., Mook, H.A., Liou, S.-H., Dowben, P.A., Plummer, E.W., (1996) Phys. Rev. B, 54, pp. R3694Zhao, G., Conder, K., Keller, H., Muller, K.A., (1996) Nature (London), 381, p. 676Oseroff, S.B., Torikachvili, M., Singley, J., Ali, S., Cheong, S.-W., Schultz, S., (1996) Phys. Rev. B, 53, p. 6521Ritter, C., Ibarra, M.R., De Teresa, J.M., Algarabel, P.A., Marquina, C., Blasco, J., García, J., Cheong, S.-W., (1997) Phys. Rev. B, 56, p. 8902Urushibara, A., Moritomo, Y., Arima, T., Asamitsu, A., Kido, G., Tokura, Y., (1995) Phys. Rev. B, 51, p. 14103Wiles, D.B., Young, R.A., (1981) J. Appl. Crystallogr., 14, p. 149Last, J.T., (1957) Phys. Rev., 105, p. 1740Silverman, B.D., Koster, G.F., (1961) Z. Phys., 163, p. 158Kim, K.H., Gu, J.Y., Choi, H.S., Park, G.W., Noh, T.W., (1996) Phys. Rev. Lett., 77, p. 1877Verelst, M., Rangavittal, N., Rao, C.N.R., Rousset, A., (1993) J. Solid State Chem., 104, p. 74Cochran, W., Zia, A., (1968) Phys. Status Solidi, 25, p. 273Thomas, H., Muller, K.A., (1968) Phys. Rev. Lett., 21, p. 1256Scott, J.F., (1969) Phys. Rev., 183, p. 823Harley, R.T., Hayes, W., Perry, A.M., Smith, S.R.P., (1973) J. Phys. C, 6, p. 2382Goodenough, J.B., Longo, J.M., (1970) Magnetic and Other Properties of Oxides and Related Compounds, 4 (PART A), p. 126. , edited by K.-H. Hellwege and A. M. Hellwege, Landolt-Borstein, Tabellen, New Series, Group 3, Springer-Verlag, BerlinElemans, A.A., Van Laab, B., Van Der Veen, K.R., Loopstra, B.O., (1971) J. Solid State Chem., 3, p. 238Iliev, M.N., Abrashev, M.V., Lee, H.-G., Popov, V.N., Sun, Y.Y., Thomsen, C., Meng, R.L., Chu, C.W., (1998) Phys. Rev. B, 57, p. 2872Wold, A., Arnott, R., (1959) J. Phys. Chem. Solids, 9, p. 176Goodenough, J.B., Wold, A., Arnott, R.J., Menyuk, N., (1961) Phys. Rev., 124, p. 373Radaelli, P.G., Cox, D.E., Marezio, M., Cheong, S.-W., Schiffer, P.E., Ramirez, A.P., (1995) Phys. Rev. Lett., 75, p. 4488Knízek, K., Jirák, Z., Pollert, E., Zounová, F., Vratislav, S., (1992) J. Solid State Chem., 100, p. 292Asamitsu, A., Moritomo, Y., Tomioka, Y., Arima, T., Tokura, Y., (1995) Nature (London), 373, p. 407Mitchell, J., Argyriou, D.N., Potter, C.D., Hinks, D.G., Jorgensen, J.D., Bader, S.D., (1996) Phys. Rev., 54, p. 6172Wollan, E.O., Koehler, W.C., (1955) Phys. Rev., 100, p. 545Udagawa, M., Kohn, K., Kashizuka, N., Tsushima, T., (1975) Solid State Commun., 16, p. 779Radaelli, P.G., Cox, D.E., Marezio, M., Cheong, S.-W., (1997) Phys. Rev. B, 55, p. 301
Microscopic electronic phase separation and metal-insulator transition in Nd0.5Sr0.5MnO3
No full textChirality-induced spin texture switching in twisted bilayer graphene
No full textThe interlayer van der Waals interaction in twisted bilayer graphene (tBLG) induces both in-plane and out-of-plane atomic displacements showing complex patterns that depend on the twist angle. In particular, for small twist angles, within each graphene layer, the relaxations give rise to a vortexlike displacement pattern which is known to affect the dispersion of the flat bands. Here, we focus on yet another structural property, the chirality of the twisted bilayer. We perform first-principles calculations based on density functional theory to investigate the properties induced by twist chirality in both real and momentum space. In real space, we study the interplay between twist chirality and atomic relaxation patterns. In momentum space, we investigate the spin textures around the K points of the Brillouin zone, showing that alternating vortexlike textures are correlated with the chirality of tBLG. Interestingly, the helicity of each vortex is inverted by changing the chirality while the different twist angles also modify the spin textures. We discuss the origin of the spin textures by calculating the layer weights and using plot regression models
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