Non-collinear ferrimagnetism in aFe64Er19B17 metallic glass

Abstract

Polarized neutron beam measurements on aFe64Er19B17 metallic glass have shown directly that it has a non-collinear magnetic structure. It can bedescribed using a model in which the magnetic moments on the iron atoms point in arandom cone that is ferrimagnetically coupled to a random cone of erbium moments, in themanner suggested from bulk measurements. The spin-flip cross-sections weresuccessfully calculated using an optimized choice of the values of the magnetic momentsμFe,μEr and the randomcone angles θFe, θEr. The non-spin-flip cross-sections have an unusual variation with the scattering vectorQ, which has not been observed before with transition metal–metalloid glasses. At 1.5and 60 K the cross-section contains a pre-peak at a smaller value ofQ (1.3 Å − 1) than the pre-peaks which have been observed in the structure factors of some transitionmetal glasses. At 180 K the form of these cross-sections remains the same but the twochannels have interchanged, so contains the pre-peak. This interchange shows that a complete inversion of the magneticstructure occurs between 60 and 180 K—presumably at the compensation temperatureTcomp≈120 K. Attempts to simulate these cross-sections using the methods applied to (Fe,Tb)B glasseswere unsuccessful because none of the known partial structure factors contains a pre-peakwhich can imitate the observed one. The possible origins of the pre-peak arediscussed.