Weak itinerant-electron ferromagnetism in amorphous Fe-Ti alloys

Abstract

In bulk Fe1-xTix alloys prepared by facing-target-type sputtering, an amorphous phase was obtained for 0.25<x<0.75. These alloys are ferromagnetic at low temperatures and the Curie temperature TC decreases with increasing x and becomes zero at x approximately=0.6. The ratio mu p/ mu s of the magnetic moment in the paramagnetic state and that at 4.2 K versus TC plot (the Rhode-Wolfarth plot) becomes very large for low TC. The square of magnetisation shows a T43/-dependence at low temperatures. Moreover, the thermomagnetic curve of the amorphous Fe1-xTix alloys with x=0.5-0.6 show no cusp at a low temperature, indicating no spin-glass ordering. Therefore the amorphous Fe1-xTix alloys are classified as random weak itinerant-electron ferromagnets. With increase in x, the residual resistivity increases, whereas the temperature coefficient of resistivity (TCR) is negative at room temperature and its absolute value increases with increasing temperature as observed in many amorphous alloys. However, the magnetic contribution to the negative TCR is prominent for x<0.6.