MAGNETIC-PROPERTIES OF THE MONOCLINIC FERH2SE4

FeRh2Se4 has been studied by x-rays, Mossbauer spectroscopy, and superconducting quantum interference device (SQUID) magnetometry. Mossbauer spectra of FeRh2Se4 have been taken at various temperatures ranging from 4.2 to 550 K. Magnetic hyperfine and quadrupole interactions at 4.2 K have been fitted, yielding the following results: H=161.6 kOe, 1/2e2qQ(1+1/3eta2)1/2=-0.93 mm/s, theta=61-degrees phi=0-degrees, and eta=0.1. The temperature dependence of the quadrupole splitting, calculated in terms of direct lattice-sum calculations using x-ray crystallographic data, is in good agreement with experimental values up to 550 K. The axial field parameter DELTA1=2.0\lambda\, the rhombic field parameter DELTA2=3.3\lambda\, and the covalency factor a 2=0.65 were obtained. Magnetic susceptibility measurements by dc SQUID magnetometry show that superexchange interactions between Fe2+ ions are antiferromagnetic.