Pressure-induced phase transition in magnetoresistance perovskite La_0.75Ca_0.25MnO₃: a GGA + U study

Abstract

Density functional theory calculations within a DFT+U approach have been carried out to determine the effect of hydrostatic pressure and strain on the structural, electronic and magnetic properties of La0.75Ca0.25MnO3. We investigate the opportunuty of the appearence of the A-type antiferromagnetic phase under pressure as observed from experiments. At ambient pressure and in the hydrostatic pressure regime (4–25 GPa), the system remains ferromagnetic in its ground state, and the A-type antiferromagnetic coupling is tied to Mn e g orbital order while the ferromagnetic behavior refers to orbital disorder one. No magnetic transition was found when increasing the hydrostatic pressure up to 25 GPa. Applying a tetragonal distortion along the b direction of the pnma orthorhombic structure, the system exhibits a transition from the ferromagnetic orbitally disordered phase to the A-type antiferromagnetic orbitally ordered phase at about 22.5 GPa, in agreement with experiment. Projected density of states (PDOS) calculations predict the pressure and strain effects that are discussed in terms of different electronic occupations through d x 2 − y 2 and d 3 z 2 − r 2 orbitals.