Susceptibility and Remanent Magnetization of a Spin Glass

We define the concentration range where a dilute alloy of transition impurities in a noble matrix is a spin glass, by the possibility of representing its properties through universal functions of the T/c and H/c variables. The susceptibility of a spin glass contains one reversible part χr which shows a sharp peak at a temperature TM ~ c. This sharp peak is due to the presence of a remanent magnetization which appears when T < TM. The remanent magnetization of a spin glass is represented by an universal curve in the reduced diagram σr = f (T/c). Its properties are like those of the remanent magnetization of monodomains. We interpret it by supposing that at T << TM a spin glass (in which the magnetic moments randomly distributed are frozen at T = 0 in random directions) is spontaneously divided in regions, each one containing in average n impurities and having a resulting moment Mg described by a Gaussian distribution ([MATH]2 = ηµ20, where µ0 is the individual magnetic moment).