Susceptibility and Remanent Magnetization of a Spin Glass

Abstract

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)

Study of spin glass and cluster ferromagnetism in RuSr2Eu1.4Ce0.6Cu2O10-δ magneto superconductor

“…Inset of Figure [32,33]. It is clear that the studied EuRu-1222 system is a typical spin-glass, with still a possibility of the existence of some inhomogeneous ferromagnetic clusters below T f, to be discussed later.…”

Weak ferromagnetism and spin-glass state with nanosized nickel carbide

“…The second description for the dynamical property of a SG phase considers the freezing transition as a nonequilibrium phenomenon. This is describable by the Vogel-Fulcher law [20], which takes into account the interacting property of the SG clusters,…”

Spin glasses in amorphous and crystalline RE alloys

“…All these findings do not favor the phase transition picture for the spin-glass freezing. In contrast, they can be interpreted rather easily within a phenomenological model of superparamagnetic clouds [3][4] inspired from Neel's studies on fine grains [14]. Such an approach is very appealing for an experimentalist by providing him with a tool for a quantitative analysis of his data.…”

“…Such an approach is very appealing for an experimentalist by providing him with a tool for a quantitative analysis of his data. In particular, the scaling behaviour observed in the dilute limit for T M and for its frequency dependence [9], for the magnetization [15][16] above T M and for the remanence [3] below T M allows the experimentalist to decide which forces are responsible (1/f 3 interactions). Nevertheless, such a model fails to account for the sharpness of the susceptibility cusp at zero field and low frequency.…”

“…-Regardless of the (short-or long-range) forces which are responsible for the spinglass phenomena [1], both dilute (~ 1 at. %, typically) and concentrated spin glasses are phenomenologically characterized by an ordering temperature below which short-range magnetic order [2] and field cooling effects are observed [3][4]. This ordering or freezing temperature T M is usually defined by a sharp cusp in zero-field ac susceptibility [5].…”