Spin reorientation, magnetization reversal, and negative thermal expansion observed in R F e0.5 C r0.5 O3 perovskites (R=Lu,Yb,Tm)

International audienceThree members of the perovskite family RFe0.5Cr0.5O3 (R=Lu,Yb, and Tm) have been synthesized and characterized. A systematic study of the crystal and magnetic structures was performed by neutron powder diffraction combined with magnetization measurements. All these compounds crystallize in a Pbnm orthorhombic unit cell and they are already antiferromagnetic at room temperature. The study of the magnetic structure vs temperature showed the occurrence of a progressive spin reorientation from Γ4TM to Γ2TM for the transition metal sublattice, and in the Tm-based sample, a long-range magnetic order of the Tm3+ sublattice was found (Γ8R). These results are in excellent agreement with the magnetic susceptibility measurements. No spin reorientation is observed in the Lu-based sample for which a magnetization reversal at a compensation temperature Tcomp=225K was detected. A clear magnetostrictive effect was observed in the samples with R=Yb and Tm associated with a negative thermal expansion and was assigned to a magnetoelastic effect produced by repulsion between the magnetic moments of neighboring transition metal ions. © 2016 American Physical Society

Magnetization reversal in mixed ferrite-chromite perovskites with non magnetic cation on the A-site

International audienceIn this work, we have performed Monte Carlo simulations in a classical model for RFe 1-x Cr x O 3 with R = Y and Lu, comparing the numerical simulations with experiments and mean field calculations. In the analyzed compounds, the antisymmetric exchange or Dzyaloshinskii-Moriya (DM) interaction induced a weak ferromagnetism due to a canting of the antiferromagnetically ordered spins. This model is able to reproduce the magnetization reversal (MR) observed experimentally in a field cooling process for intermediate x values and the dependence with x of the critical temperatures. We also analyzed the conditions for the existence of MR in terms of the strength of DM interactions between Fe 3+ and Cr 3+ ions with the x values variations. © 2016 IOP Publishing Ltd

Synthesis of new double perovskites La 1.98 Mn 1.11 Mo 0.89 O 5.93 and La 1.92 Mn 1.29 Mo 0.71 O 5.84 : Characterization of structural and magnetic properties

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Straightforward high-pressure synthesis and characterization of indium-based thiospinels: photocatalytic potential for hydrogen production

Ternary chalcogenides (ABX) based on the spinel structure are gaining a great deal of attention because of the possibility of tuning their magnetic and optoelectronic properties not only by changing chemical composition but also by altering their degree of inversion. Here we report a rapid high-pressure synthetic method for the synthesis of MInS powders starting from commercially available solid sulfides. We prove the versatility of our method by reporting the synthesis of six members of the MInS family (M = Mn, Fe, Co, Ni, Zn, and Cd) under high-pressure conditions (3.5 GPa); these compounds show complete to moderate degrees of inversion. Furthermore, this family covers a spectral region that includes visible band gaps. Interestingly, the structural refinement carried out by X-ray and neutron diffraction allows one to establish positive correlations between the gap and different parameters, including the degree of inversion. Finally, as a proof-of-concept, these ternary chalcogenides show moderate photocatalytic hydrogen production from aqueous solutions.The authors thank the Spanish Ministerio de Economía y Com-petitividad (MINECO) for financial support through the projectsMAT2013-41099-R, CTQ2013-48669-P, and MAT2014-54994-R.R. E. C. acknowledges support from the Consejo Nacionalde Investigaciones Científicas y Técnicas (CONICET) (PIP#11220120100360), the Agencia Nacional de Promoción Científ-ica y Tecnológica (ANPCyT) (PICT-2013-2149), and the Secretariade Ciencia y Tecnología de la Universidad Nacional de Cordoba(SECyT-UNC) (project 203/14). J. P.B. is grateful for a fellowshipfrom CONICET. MINECO/ICTI2013-2016/CTQ2013-48669-P MINECO/ICTI2013-2016/MAT2014-54994-

Raman And Infrared Spectroscopy Of Sr2b′uo6 (b′ = Ni; Co) Double Perovskites

Temperature dependent normal modes and lattice thermal expansion of Sr 2B′UO6 (B′ = Ni, Co) double perovskites were investigated by Raman/infrared spectroscopies and synchrotron X-ray diffraction, respectively. Monoclinic crystal structures with space group P21/n were confirmed for both compounds, with no clear structural phase transition between 10 and 400 K. As predicted for this structure, the first-order Raman and infrared spectra show a plethora of active modes. In addition, the Raman spectra reveal an enhancement of the integrated area of an oxygen stretching mode, which is also observed in higher-order Raman modes, and an anomalous softening of ∼1 cm-1 upon cooling below T* ∼ 300 K. In contrast, the infrared spectra show conventional temperature dependence. The band profile phonon anomalies are possibly related to an unspecified electronic property of Sr2B′UO6 (B′ = Ni, Co). © 2010 Elsevier B.V. All rights reserved.542142147Serrate, D., Serrate, D., De Teresa, J.M., Ibarra, M.R., (2007) J. Phys.: Condens. Matter, 19, p. 023201Kobayashi, K.-I., Kimura, T., Sawada, H., Terakura, K., Tokura, Y., (1998) Nature (London), 395, p. 677Kobayashi, K.I., Kimura, T., Tomioka, Y., Sawada, H., Terakura, K., (1999) Phys. Rev. B, 59, p. 11159Prellier, W., Smolyaninova, V., Biswas, A., Galley, C., Greene, R.L., Ramesha, K., Gopalakrishnan, J., (2000) J. Phys. C, 12, p. 965Gopalakrishnan, J., Chattopadhyay, A., Ogale, S.B., Venkatesan, T., Greene, R.L., Millis, A.J., Ramesha, K., Marest, G., (2000) Phys. Rev. B, 62, p. 9538Maignan, A., Raveau, B., Martin, C., Hervieu, M., (1999) J. Solid State Chem., 144, p. 224Dai, J.M., Song, W.H., Wang, S.G., Ye, S.L., Wang, K.Y., Du, J.J., Sun, Y.P., Gao, B.J., (2001) Mat. Sci. Eng. B, 83, p. 217Granado, E., Hung, Q., Lynn, J.W., Gopalakrishnan, J., Greene, R.L., Ramesha, K., (2002) Phys. Rev. B, 66, p. 064409Azimonte, C., Cezar, J.C., Granado, E., Huang, Q., Lynn, J.W., Campoy, J.C.P., Gopalakrishnan, J., Ramesha, K., (2007) Phys. Rev. Lett., 98, p. 017204Azimonte, C., Granado, E., Cezar, J.C., Gopalakrishnan, J., Ramesha, K., (2007) J. Appl. Phys., 101, pp. 09H115Serrate, D., De Teresa, J.M., Algarabel, P.A., Galibert, J., Ritter, C., Blasco, J., Ibarra, M.R., (2007) Phys. Rev. B, 75, p. 165109Sikora, M., Mathon, O., Van Der Linden, P., Michalik, J.M., De Teresa, J.M., Kapusta, C., Pascarelli, S., (2009) Phys. Rev. B, 79, p. 220402Pinacca, R.M., Viola, M.C., Pedregosa, J.C., Muñoz, A., Alonso, J.A., Martínez-Lope, M.J., Carbonio, R.E., (2005) Dalton Trans., p. 447Pinacca, R.M., Viola, M.C., Pedregosa, J.C., Martínez-Lope, M.J., Carbonio, R.E., Alonso, J.A., (2007) J. Solid State Chem., 180, p. 1582Ferreira, F.F., Granado, E., Carvalho Jr., W., Kycia, S.W., Bruno, D., Droppa Jr., R., (2006) J. Synchrotron Rad., 13, p. 46Larson, A.C., Von Dreele, R.B., (2000) Los Alamos National Laboratory Report LAUR 86-748Toby, B.H., (2001) J. Appl. Cryst., 34, pp. 210-213Prosandeev, S.A., Waghmare, U., Levin, I., Maslar, J., (2005) Phys. Rev. B, 71, p. 214307Iliev, M.N., Abrashev, M.V., Litvinchuk, A.P., Hadjiev, V.G., Guo, H., Gupta, A., (2007) Phys. Rev. B, 75, p. 104118Balkanski, M., Wallis, R.F., Haro, E., (1983) Phys. Rev. B, 28, p. 1928Andreasson, J., Holmlund, J., Knee, C.S., Käll, M., Börjesson, L., Naler, S., Bäckström, J., Eriksson, S.-G., (2007) Phys. Rev. B, 75, p. 104302Fujioka, Y., Frantti, J., Kakihana, M., (2004) J. Phys. Chem. B, 108, p. 17012Fujioka, Y., Frantti, J., Kakihana, M., (2006) J. Phys. Chem. B, 110, p. 777Kurosawa, T., (1961) J. Phys. Soc. Jpn., 16, p. 1208Siny, I.G., Katiyar, R.S., Bhalla, A.S., (2000) Ferroelectr. Rev., 2, p. 51Granado, E., García, A., Sanjurjo, J.A., Rettori, C., Torriani, I., Prado, F., Sánchez, R.D., Oseroff, S.B., (1999) Phys. Rev. B, 60, p. 11879Iliev, M.N., Guo, H., Gupta, A., (2007) Appl. Phys. Lett., 90, p. 15191