Spin reorientation, magnetization reversal, and negative thermal expansion observed in RFe0.5Cr0.5O3 perovskites (R = Lu,Yb,Tm)

Abstract

Three members of the perovskite family RFe0.5Cr0.5O3 (R = Lu,Yb, and Tm) have been synthesized and characterized. A systematic study of the crystal and magnetic structures was performed by neutron powder diffraction combined with magnetization measurements. All these compounds crystallize in a Pbnm orthorhombic unit cell and they are already antiferromagnetic at room temperature. The study of the magnetic structure vs temperature showed the occurrence of a progressive spin reorientation from TM 4 to TM 2 for the transition metal sublattice, and in the Tm-based sample, a long-range magnetic order of the Tm3+ sublattice was found (R 8 ). These results are in excellent agreement with the magnetic susceptibility measurements. No spin reorientation is observed in the Lu-based sample for which a magnetization reversal at a compensation temperature Tcomp = 225 K was detected. A clear magnetostrictive effect was observed in the samples with R = Yb and Tm associated with a negative thermal expansion and was assigned to a magnetoelastic effect produced by repulsion between the magnetic moments of neighboring transition metal ions.