The Magnetic Behaviors of Spin-Glass $\hbox{FeGa}_{2}\hbox{O}_{4}$ System

Abstract

We present the investigation of magnetic properties of spin-glass FeGa2O4 system. From X-ray diffraction patterns of FeGa2O4, refined with Rietveld's refinement method, its structure is determined to be cubic spinel with space group Fd - 3m and the lattice parameter of α0 = 8.385 Å. From temperature-dependent magnetization curves under 1000 Oe, the Neel temperature is found to be TN = 14 K, which coincides with the value obtained from the Mossbauer spectrum. The freezing temperature Tf of the sample shifts to higher temperature with increasing frequency, as seen in conventional metallic spin glasses. Also, we have determined the small activation energy, Ea of 1.04266 × 10-4 meV from Arrhenius law v = v0 exp(-En/kBTf), where kB is Boltzmann constant, and Ea is activation energy. The Mossbauer spectrum at 4.2 K shows severely distorted 8-line shape coming from frozen spin-disorder state and an incommensurate spin structure, as in spin glasses. The change in the electric quadrupole shift above Tf is caused by the presence of the maximum electric dipole interaction among frozen disordered spins around Tf as in spin-glass material, and charge re-distribution from spin-relocation arising above TN.