Influence of the external pressure on the structure and magnetic properties of Nd0.5Sr0.5CoO3 cobaltite

JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS

卷:504

Article

Torrao, R.¹  Caraballo Vivas, R. J.^1,5  Pimentel, B.¹  Santos, M. C.^1,2  Paixao, L. S.³  dos Santos, A. M.⁴  Reis, M. S.¹  Rocco, D. L.^1,2 

[1] Univ Fed Fluminense, Inst Fis, Av Gal Milton Tavares de Souza S-N, BR-24210346 Niteroi, RJ, Brazil

[2] Ctr Fed Educ Tecnol Minas Gerais CEFET MG, Dept Formacao Geral, Campus Timoteo, BR-35180008 Timoteo, MG, Brazil

[3] Univ Estadual Campinas, Inst Fis Gleb Wataghin, BR-13083859 Campinas, SP, Brazil

[4] Oak Ridge Natl Lab, Neutron Scattering Div, POB 2009, Oak Ridge, TN 37831 USA

[5] Ctr Brasileiro Pesquisas Fis, Rua Dr Xavier Sigaud 150, BR-22290180 Rio De Janeiro, Brazil

关键词: Cobaltites;    Magnetic properties;    Anomalous XRD;    Pressure;    Syncrotron;    Magnetocaloric effect;   

DOI  :  10.1016/j.jmmm.2020.166678

来源: Elsevier

【 摘 要 】

The magnetic properties of the compound-type cobaltites LnACoO(3 )(Ln = Lanthanide and A = alkaline-earth) are extremely dependent on the structural deformation, which can be induced by either chemical substitution or applying pressure. These two approaches are not equivalent because the atomic substitution changes the ratio of Co3+ and Co4+. It is well known that the additional electron of Co3+ plays a fundamental role in the magnetic and electric properties of these materials. Thus, the pressure is a way to influence the magnetic and electric properties considering only the structural deformation. In this work, pressure was applied to deform the structure of Nd0.5Sr0.5CoO3 and, thus, to elucidate its effect on the structural and magnetic properties. The findings show that even under pressure of 50 kbar, no structural phase transition was detected, but the unit cell volume significantly decreases by 2.8% and the Co-O-1-Co bond angle increases by 2.6%. However, the elasticity parameter (defined as the Co-O apical distance divided by the square root of the octahedral basal area) remained constant over the pressure range. The magnetic properties were evaluated up to 10.9 kbar, and the findings show that T-c varies with a rate of 0.5 K/kbar, and that the magnetic entropy change of the compound remains almost constant at a value of - 2 J/kg K for 5 T of magnetic field variation. The Co3+ and Co4+ ions were found to be in an intermediate spin state and remain the same over all studied pressure interval. To conclude, the structural deformation induced by the high pressure seem to not affect the magnetic properties, and the elasticity parameter is a useful tool sensitive to this change. These results indicate that, for strongly correlated electron system, the ratio of Co3+ and Co4+ is much more critical for changing the magnetic properties than the structural deformation.

【 授权许可】

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