Local inversion symmetry breaking and spin-phonon coupling in the perovskite GdCrO3

Abstract

Our detailed temperature-dependent synchrotron powder x-ray diffraction studies along with first-principles density-functional-theory-based calculations enable us to shed light on the origin of ferroelectricity in GdCrO3. The actual lattice symmetry is found to be the noncentrosymmetric orthorhombic Pna2(1) structure, supporting the polar nature of the system. Polar distortion is associated with the Gd displacements with respect to the oxygen cage. Our study reveals an intimate analogy between GdCrO3 and YCrO3. However, a distinctive difference exists because Gd is less displacive than Y, which results in an orthorhombic Pna2(1) structure in GdCrO3 in contrast to the monoclinic P2(1) structure in YCrO3 and, consequently, decreases its polar property. It is found that magnetic coupling between Gd 4f and Cr 3d plays an important role in ferroelectric distortion. A strong magneto-electric coupling is also revealed using Raman spectroscopy based analysis, indicating its relevance to ferroelectric modulation.