Frequency Dependence of the AC Susceptibility of the Reentrant System CdCr_2xIn_2−2xS₄ (0.85 < x ≦ 1)

Abstract

on the occasion of his 80th birthday AC permeability measurements of the reentrant spin glass system CdC:r2,In2-,S4 (0.85 < x 1) are performed on toroidal shaped samples by using the transformer technique since the demagnetizing factor is minimized. The complex permeability observed is very close to the true initial permeability. The abrupt decrease of p' a t low temperatures is an intrinsic effect, probably related to the transition to the reentrant spin glass state. The out-of-phase permeability presents a maximum a t the transition temperature TRSG. The frequency dependence of 2'1~s~ is studied (130 Hz 5 5 v 5 100 kHz). Its variation corresponds with the explanation of reentrant properties based on the existence of clusters of which the freezing destroys the ferromagnetic order.En utilisant la mkthode du transformateur, des mesures de permkabilitk alternative ont Cte effectukes sur des bchantillons en forme de tore du systhme rbentrant verre de spin CdCr2,Inz -,S, (0,85 < x 1). Le facteur dkmagnktisant &ant minimisb, la permkabilitb complexe observbe est trhs proche de la permkabilitb initiale intrinshque. A basse tempbrature, la dkcroissance rapide de p' est un effet intrinshque, probablement relib A la transition vers un &tat spin glass rbentrant.La partie complexe de la permkabiliti: prksente un maximum B la tempkrature de transition TRSG.La variation de TRSG avec la frkquence a Otk btudibe (130 Hz 5 v 5 100 kHz); elle est en accord avec l'interprbtation des propribtbs rbentrantes basCe sur l'existence de clusters dont le gel dbtruit l'ordre ferromagnbtique.

Understanding the spin glass transition as a dynamic phenomenon

“…On the other hand, when t < τ in the short-time spin-wave regime, magnetic response is governed by Eqs. ( 8) and (10). This gives χ = χ sw at and below T g :…”

“…Experiments widely show strong dynamic effects. T g significantly increases with field frequency, or as observation time decreases [1,[9][10][11][12][13][14][15][16][17][18][19][20]. This is inconsistent with a transition between two equilibrium phases [1].…”

Magnetic structure and phase diagram of the frustrated spinel Cd1−xZnxCr2Se4

“…In our case, the relative size of the shift and the closeness of T 0 and T fg characterises rather a spin-glass like transition. Various criteria of the frequency dependence of T fg have been suggested to distinguish between a true thermodynamic transition (true spin-glass) or a dynamic non-equilibrium process (progressive freezing of cluster moments) [31]. The obtained parameters: DT fg /T fg D log f ¼ 0.07, (T fg ÀT 0 )/T fg ¼ 0.3 and E a /kT fg ¼ 2.2(T fg ¼ 12.8 K at 995 Hz), indicate an intermediate behaviour between a cluster regime and a true spin-glass regime; the observed re-entrant transition to spin-glass state being explained as a freezing of finite clusters which destroys the ferromagnetic order.…”

IV‐VI Ferromagnetic Semiconductors — Recent Studies

“…The values of R reported for known spin glass systems range from 0.005 (Cu) to 0.11 (La 1-x Gd x Al 2 [9]) and the rate of the change in Im(χ) is the same as the rate of the change in…”