Magnetic properties of iron-rich Fe-Zr glasses

A systematic study of the magnetic properties of melt-spun amorphous Feₓ{Zr}_{100{{-}}x}alloys with 88≤x≤93 using M\"ossbauer and magnetization measurements has established the magnetic phase diagram. The ordering temperature{T}c$ falls sharply with increasing x; below a second transition ${T}xy$, associated with the freezing of transverse-spin components, all the alloys order asperomagnetically (${T}xyTc). Hysteresis appears at still lower temperatures, but it is not directly related to the transverse-spin freezing. A T1.3 variation of hyperfine field observed for TTxy is attributed to excitation of transverse magnetic modes. Contrary to the predictions of Heisenberg spin-glass theory, neither the ferromagnetic nor the asperomagnetic order appears to be long range. Extrapolation to x=100 indicates that pure amorphous iron would be a speromagnet with an iron moment of 1.7μB and a spin-freezing temperature of order 150 K. Upon hydrogenation the magnetic structures of all the a-Fe-Zr alloys lose their noncollinear character, becoming good ferromagnets with Curie points in excess of 400 K.