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

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 T_N = 14 K, which coincides with the value obtained from the Mossbauer spectrum. The freezing temperature T_f 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, E_a of 1.04266 × 10^-4 meV from Arrhenius law v = v₀ exp(-E_n/k_BT_f), where k_B is Boltzmann constant, and E_a 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 T_f is caused by the presence of the maximum electric dipole interaction among frozen disordered spins around T_f as in spin-glass material, and charge re-distribution from spin-relocation arising above T_N.