Abstract: Magnetic and transport properties of metglas Fe40Ni38Mo4B18

Abstract

Systematic studies of the magnetic susceptibility, the ferromagnetic anisotropy of resistivity (FAR) and the Hall effect are lacking in the amorphous ferromagnet Fe40Ni38Mo4B18 (Metglas 2826 MB). Lowfield susceptibility has been measured between 300 K to 1000 K in the amorphous, thermally cycled and crystallized states. The kink-point method yields Tc=589 K while −dμ/dT vs T plot gives Tc=593 K in the amorphous state. Differential thermal analysis shows no crystallization below 720 K. A thermal cycling up to 1000 K at a heating rate of 3 K/min produces two crystalline magnetic phases with Tc= (760±10) K and (545±5) K. Samples annealed at 1000 K for 4 hrs also show the same two phases, only the transitions are somewhat sharper. Longitudinal and transverse magnetoresistivity curves are very similar to that of the crystalline ferromagnets. The FAR is very small and positive with a typical value of 0.1%. The average negative slope at high fields, due to less electron–magnon scattering, changes from −1.1×10−8 gauss−1 to −0.55×10−3 gauss−from 300 K to 77 K. The values of FAR, the high-field slopes, the electrical resistivity, the Hall constants and the Hall conductivity will be compared with those of other metal glasses and their crystalline counterparts. The negative transverse magnetoresistance δR/Ro=−4.5×10−4 is found to be roughly proportional to β2 where β = the tangent of the Hall angle = 2.2×10−2. This result, together with the existing data for other metal glasses will be interpreted in terms of the existence of one easy axis of magnetization associated with the anisotropy energy and the decrease of ρ with the removal of domain walls.