INTERSUBLATTICE F-D EXCHANGE INTERACTION IN THE INTERMETALLIC LAVES PHASE-COMPOUNDS Y1-TGDT(CO1-XALX)2

Systems Y1-tGdt(Co1-xAlx)2 with x = 0.05, 0.07, 0.085, 0.105 and 0 less-than-or-equal-to t less-than-or-equal-to 0.2 are studied to ascertain the influence of the intersublattice f-d exchange interaction on the magnetic behaviour of itinerant metamagnets Y(Co1-xAlx)2. The field of the metamagnetic transition decreases when the Gd-concentration is increased for the compounds with x greater-than-or-equal-to 0.07, and then a ferrimagnetic state is stable for more Gd-substitutions. Results obtained are explained in the molecular field approximation taking into consideration the itinerant metamagnetism of the d-electron subsystem. Intersublattice molecular field coefficient lambda(fd) is determined from both Gd-concentration dependence on the critical field of the metamagnetic transition and values of the critical field of the rise of a non-collinear magnetic structure in high external magnetic fields. The same value of lambda(fd) = 640 kOe/mu(B) f.u. is obtained by different methods.