Spin reorientation, magnetization reversal, and negative thermal expansion observed in R F e0.5 C r0.5 O3 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 Γ4TM to Γ2TM for the transition metal sublattice, and in the Tm-based sample, a long-range magnetic order of the Tm3+ sublattice was found (Γ8R). 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=225K 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. © 2016 American Physical Society.