Heisenberg spin-glass behaviour in Ga^sub 0.99^ Yb^sub 0.01^ FeO^sub 3

The dynamic and static magnetic properties of Ga0.99Yb0.01FeO3 are studied in detail using ac susceptibility and dc magnetization measurements. The study shows that the compound undergoes a spin-glass freezing at Tg≈213K. The dynamic scaling analysis of ac susceptibility data reveals typical features characteristic of canonical spin-glasses, i.e., relaxation time τ*~10-14s, critical exponent νz=4.1±0.2, and frequency sensitivity parameter δf~10-3 within three frequency decades. The analysis of the critical behaviour of the static nonlinear susceptibility yields the critical exponents γ=4.3±0.1,β=1.0±0.1, and δ=5.5±0.5, which lie between those typical of three-dimensional (3D) weakly anisotropic Heisenberg and Ising spin glasses. The analysis of the field-cooled and zero-field-cooled magnetization data allows to define two characteristic temperatures depending on the applied magnetic field. The upper one, Tirr(H), is the threshold temperature corresponding to the appearance of weak irreversibility, whereas the lower one, Ts(H), marks the onset of strong irreversibility. The resulting field-temperature phase diagram turns out to be in good quantitative agreement with the mean-field predictions for 3D Heisenberg spin-glass with random magnetic anisotropy, and appears consistent with the chiral driven freezing scenario.