CRITICAL LINES OF MAGNETIC SEMICONDUCTOR THIN-FILMS - EXPERIMENT

The irreversibilities between the field-cooled and zero-held-cooled de magnetization were used to determine the field and composition depend ence of the spin-glass freezing temperature in CdCr(2-2x)ln(2x)Se(4) t hin films. The magnetic ordering was confirmed by the temperature depe ndence of induced magnetization M and unidirectional magnetic anisotro py held H-an determined from ferromagnetic resonance data (4.2-120 K). The experimentally determined H-T phase diagram shows two instability lines: the Gabay-Toulouse-type (GT line) and the Almeida-Thouless-typ e (AT line) for thin films of CdCr2Se4:In with reentrant transition an d the AT line for CdCr2-2xIn2xSe4 in the spin-glass state. The AT and GT lines obey the relation tau=[(n+1)(n+2)/8](1/3) (h(eff))(2/3) and t au=[(n(2)+4n+2)/(4(n+2)(2))] (h(eff))(2), respectively, for the normal ized effective field h(eff)=h(a)+h(m). The first term in h(eff) stands for the external magnetic held, while the second is related to the in ternal field of the infinite ferromagnetic network (long-range orderin g). The value of h(m) determined from the H-T phase diagram was found to be dependent on indium concentration.