Structural, electrical, magnetic, and electronic structure studies of PrFe_(1-x)Ni_xO_3 (x≤0.5)

摘要

We report the x-ray absorption studies on O K, Fe L_(3,2), Ni L_(3,2), and Pr M_(5,4) edges in PrFe_(1-x)Ni_xO_3 along with their structural, electrical transport, and magnetization characterizations. All the samples are in single phase having orthorhombic structure with space group Pnma for x≤ 0.4. Ni doping at Fe site brings the system in the conducting regime, resistivity decreases from GΩ cm to 260 mΩ cm at room temperature, and the magnetic ordering is stabilized. The temperature dependent resistivity follows the semiconducting behavior and fits well with Greaves' variable range hopping model. The gap parameter is reduced from 2 to 0.118 eV. The materials are in weak ferromagnetic state and magnetization is gradually decreasing with the enhancement of Ni substitution, whereas magnetic anisotropy is reduced substantially. A new feature about 2.0 eV lower than the pre-edge of PrFeO_3 in O K edge is observed with Ni substitution at Fe site due to the 3d contraction effect and is growing with the increase of Ni substitution. From 2p edges (L_(3,2) edges) of Fe and Ni, it is confirmed that both are in trivalent state and Ni is in mixed spin state with 3d~7 (_(2g)~5,e_g~2 and t_(2g)~6,e_g~1) configuration in ground state. The trivalent state of Pr is confirmed by x-ray absorption spectroscopy of Pr at M_(5,4) edges. These observations have been explained on the basis of charge carrier doping in PrFeO_3 with the Ni substitution. The disorder induced localization is found to control the conductivity and magnetism in the present materials. The controlled doping of carriers in semiconducting regime and ferromagnetism propose these materials as a promising candidate for the spintronic applications.