Re-Entrant Spin Reorientation Transition And Griffiths-Like Phase In Antiferromagnetic Tbfe0.5cr0.5o3

The perovskite TbFe0.5Cr0.5O3 shows two anomalies in its magnetic susceptibility at T-N = 257 K and T-SR = 190 K which are, respectively, the antiferromagnetic and spin-reorientation transition that occur in the Fe/Cr sublattice. Magnetic susceptibility of this compound reveals canonical signatures of a Griffiths-like phase: a negative deviation from the ideal Curie-Weiss law and in less-than-unity power-law susceptibility exponents. Neutron-diffraction data analysis confirms two spin-reorientation transitions in this compound. The first one from Gamma(2) (C-x, G(y), F-z) to Gamma(4) (A(x), F-y, G(z)) occurs at T-N = 257 K and a second one from Gamma(4) (A(x), F-y, G(z)) to Gamma(2) (C-x, G(y), F-z) at T-SR = 190 K in the Pnma space-group setting. The Gamma(2) (C-x, G(y), F-z) structure is stable down to 7.7 K, leading to an ordered moment of 3.34(1) mu(B)/Fe3+ (Cr3+). In addition to the long-range magnetic order, experimental indication of diffuse magnetism is observed in neutron-diffraction data at 7.7 K. Tb develops a ferromagnetic component along the z axis at 20 K. Thermal conductivity and spin-phonon coupling of TbFe0.5Cr0.5O3 studied through Raman spectroscopy are also presented in the paper. The magnetic anomalies at T-N and T-SR do not appear in the thermal conductivity of TbFe0.5Cr0.5O3, which appears to be robust up to 9 T. On the other hand, they are revealed in the temperature dependence of full-width-at-half-maximum curves derived from Raman intensities. An antiferromagnetic structure with up arrow down arrow up arrow down arrow arrangement of Fe/Cr spins is found as the ground state through first-principles energy calculations, supporting the experimentally determined magnetic structure at 7.7 K. The spin-resolved total and partial density of states show that TbFe0.5Cr0.5O3 is insulating with a band gap of similar to 0.12 (2.4) eV within GGA (GGA+U) functionals.