Tuning magnetic coercivity with external pressure in iron-rhenium based ferrimagnetic double perovskites

摘要

We studied the effect of physical pressure on the electronic and magnetic properties of ferrimagnetic double perovskites A_2FeReO_6 (A = Ca, Ba) using Re L_(2,3) edge x-ray absorption spectroscopy and powder diffraction measurements. Volume compression is shown to dramatically increase the magnetic coercivity (H_c) in polycrystalline samples of both compounds with ΔH_c/ΔV ～ 150-200 Oe/A~3. A nearly eight-fold increase in H_c, from 0.2 to 1.55 T, is obtained in Ba_2FeReO_6 at P = 29 GPa. While no signs of structural phase transitions are seen in either sample to ～30 Gpa, the structural data points to a pressure-driven increase in tetragonal distortion of ReO_6 octahedra. A sizable but pressure-independent Re orbital-to-spin magnetic moment ratio is observed, pointing to the critical role of spin-orbit interactions at Re sites. We present a j_(eff) description of the electronic structure that combines effects of crystal field and spin-orbit coupling on the Re 5d~2 orbitals and use this description to provide insight into the pressure-induced enhancement of magnetic anisotropy.