Magnetic coupling in amorphous Fe80-xGdxB20 alloys

Amorphous Fe80-xGdxB20 alloys have been prepared by melt spinning and their magnetic properties have been studied. Mean-field theory has been used to explain the temperature dependence of the magnetization. High-field magnetization studies on samples with stoichiometry dose to that of a compensated ferrimagnet show a magnetic behaviour that is characteristic of a non-collinear magnetic structure of the Gd and Fe sublattices. From the noncollinear regime the exchange interaction between the Fe and Gd magnetic sublattices have been evaluated. The J(GdFe) values derived in this way are compared with values of the exchange interactions obtained by mean-field theory. The region of the canted moments can be described by a phase diagram in H-T plane. (C) 2000 Elsevier Science B.V. All rights reserved.