Magnetic moment and spin state transition on rare monovalent iron ion in nitridoferrate Ca6Li0.5Fe0.5Te2N3

By first principles simulation, we studied the magnetic properties of Ca-6(Li0.5Fe0.5) Te2N3 including the spin moment, orbital moment, and pressure-driven spin state transition of Fe ion from the high-spin (S = 3/2) to the low-spin (S = 1/2) state. Our spin-polarized calculations have correctly revealed that Ca-6(Li0.5Fe0.5) Te2N3 is a magnetic semiconductor with a band gap of 0.49 eV. The spin moment around the Fe ion with a 3d(7) configuration is 3.0 mu B, and the orbital moment is 0.15 mu B, which is contrary to the large orbital moment suggested by experiment. With increasing pressure, a high-spin to low-spin state transition with an Fe moment collapse from 3 mB to 1 mB occurs at 18 GPa, accompanied by a semiconductor to metal transition. The underlying mechanism is explained in terms of the interplay between the crystal field and the electron population of the Fe 3d orbitals.