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

We present the investigation of magnetic properties of spin-glass FeGa
₂
O
₄
system. From X-ray diffraction patterns of FeGa
₂
O
₄
, refined with Rietveld's refinement method, its structure is determined to be cubic spinel with space group Fd - 3m and the lattice parameter of α
₀
= 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 = v
₀
exp(-E
_n
/k
_B
T
_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
.