Optical and magnetic properties of Gd_1−x Sr _x CrO₃ (0  ⩽  x  ⩽  0.15)

Abstract

Optical and magnetic properties of Gd1−xSrxCrO3 (0 ⩽ x ⩽ 0.15) polycrystalline samples have been investigated to identify the role of Sr2+ ion in GdCrO3 compound. Quantitative structural analysis using Rietveld refinement suggests the formation of single orthorhombic phase up to x = 0.1 composition, and in addition, a secondary monazite-type structure of SrCrO4 arises for x = 0.15 composition. Raman and Fourier transform infrared spectra also confirm the presence of SrCrO4 component for higher concentration of Sr2+ ion. Mixed valence state of Cr such as Cr3+ and Cr4+ is obtained from x-ray photoelectron spectroscopy. The presence of Cr4+ ion induces a reduction of optical band gap with increase of Sr content. The unoccupied states originate from Cr4+ modify d–d transitions. Larger cell volume and breaking of magnetic exchange pathways through nonmagnetic element (Sr) weaken the strength of interaction and consequently lower Néel and spin reorientation temperatures.