FIELD-INDUCED MAGNETIC PHASE-TRANSITIONS IN A FERRIMAGNET WITH ONE UNSTABLE MAGNETIC SUBSYSTEM

The magnetization of the f-d ferrimagnet Y0.75Tm0.25(Co0.88Al0.12)2 wi th an unstable metamagnetic itinerant d-subsystem in the strongly ferr omagnetic state was measured up to 38 T at 4.2 K. Two metamagnetic tra nsitions connected with sequential demagnetizing and re-entrant magnet izing of the d-subsystem were observed. The experimental results are i n good agreement with the theoretical M(H) dependence calculated for t he f-d exchange coefficient lambda(fd) = -16.4 T/mu(B) f.u., the Tm ma gnetic moment mu(f) = 4.3 muB and with the use of the experimental M(H ) curve of Y(Co0.88Al0.12)2. The bend between the two metamagnetic tra nsitions observed in the experimental curve was interpreted, acccordin g to calculations, as a region where the noncollinear phase exists.