Dynamic evidence for a 2 d-3 d crossover in the Ising spin glass Fe 0 . 35 Mg 0 . 65 Br 2

2014 We report on magnetic dynamic properties in the Ising spin glass Fe0.35Mg0.65Br2. The ac susceptibility curves have been deduced from direct susceptibility and Faraday rotation measurements over a wide frequency range extending from 100 kHz down to 0.05 Hz. The temperature dependence of the characteristic relaxation time cannot be fitted by either a power or an Arrhenius law over the whole frequency range. We show that this system exhibits a dimensional 2d-3d crossover when lowering the temperature. J. Phys. France 50 (1989) 3441-3445 15 DÉCEMBRE 1989,