ITINERANT METAMAGNETISM IN F-D SYSTEMS

We have investigated magnetic state of itinerant f-d ("rare earth"-"transition metal") ferrimagnetic within the framework of self-consistent spin-fluctuation theory. A particular feature of the theoretical model under consideration was that both the localized f-magnetic moments and the itinerant d-sublattice excitations (fluctuations in k-space) were taken into account to calculate the free energy (FE) of the system. Therefore, the FE expansion coefficients, which are known to be slowly dependent on the temperature T (if we neglect fluctuations), are renormalized twice. It determines the behavior of the system at different magnetic fields and temperatures. The results are presented as a magnetic phase diagram in "field-temperature" (H-T) coordinates. The important feature of this phase diagram is the possibility of the reversal metamagnetic transition induced by magnetic field.