Eur. Phys. J. B (2013) 86: 360
https://doi.org/10.1140/epjb/e2013-40438-y

Regular Article

Pressure-induced structural transformations, orbital order and antiferromagnetism in La_0.75Ca_0.25MnO₃

¹ Frank Laboratory of Neutron Physics, JINR, 141980 Dubna, Russia
² Tula State University, Natural Sciences Department, 300600 Tula, Russia
³ Institute of Physics, Academy of Sciences, 16253 Prague, Czech Republic
⁴ Bayerisches Geoinstitut, Universität Bayreuth, 95440 Bayreuth, Germany
⁵ Institute for Metal Physics, Ural Division of RAS, 620219 Yekaterinburg, Russia

^a e-mail: ekich@nf.jinr.ru

Received: 25 April 2013
Published online: 28 August 2013

Abstract

High pressure evolution of structural, vibrational and magnetic properties of La_0.75Ca_0.25MnO₃ was studied by means of X-ray diffraction and Raman spectroscopy up to 39 GPa, and neutron diffraction up to 7.5 GPa. The stability of different magnetic ground states, orbital configurations and structural modifications were investigated by LDA  +  U electronic structure calculations. A change of octahedral tilts corresponding to the transformation of orthorhombic crystal structure from the Pnma symmetry to the Imma one occurs above P ~ 6 GPa. At the same time, the evolution of the orthorhombic lattice distortion evidences an appearance of the e_gd_{x² − z²} orbital polarization at high pressures. The magnetic order in La_0.75Ca_0.25MnO₃ undergoes a continuous transition from the ferromagnetic 3D metallic (FM) ground state to the A-type antiferromagnetic (AFM) state of assumedly 2D pseudo-metallic character under pressure, that starts at about 1 GPa and extends possibly to 20–30 GPa.