Experimental study of the spin freezing in an insulating spin-glass: Static and dynamical aspects

We present here a detailed study of the ac susceptibility and nonlinear dc magnetization in the vicinity of Tf in an insulating spin-glass with short-range magnetic interactions, manganese amorphous aluminosilicate. The variation of the freezing temperature Tf with the measuring frequency ν between 13.5 Hz and 4 MHz can be interpreted by a Fulcher law, but in a wide range of the characteristic parameters τ₀ and T₀. The behavior of the in-phase and out-of-phase components χ^' and χ^'' of the ac susceptibility is consistent with a large distribution of relaxation times. The dc magnetizations were studied by means of a superconducting quantum interference device and a fluxmeter in applied fields ranging from 0.01 to 1000 Oe. The rapid increase of the nonlinear susceptibility when approaching Tf is in agreement with the mean-field theory of spin-glasses. We then show that the experimental results can be described by the scaling relation χS(H,ε)=H^2δF(εH^2φ) and determine the scaling exponents δ=5±1 and φ=1.1±0.2.