Amorphous yttrium-iron alloys. I. Magnetic properties

Abstract

The magnetic properties of amorphous yttrium-iron alloys Y1-xFex have been studied over a wide concentration range 0.32<or=x<or=0.88. Appearance of a moment on the iron in the region x=0.2-0.4 is associated with band metamagnetism, just as for cobalt or nickel alloys. An yttrium-rich alloy (x=0.32) shows exchange-enhanced Pauli paramagnetism in large applied fields. In the other samples, the temperature variation of the susceptibility is not reversible below a temperature TH, but the susceptibility maximum occurs at a lower temperature, TM. These properties are characteristic of a spin glass. Competing exchange interactions of both signs, which stabilise helimagnetic structures in some crystalline R2F17 alloys, lead in the amorphous state to spin-glass behaviour and asperomagnetic order. The dominant positive interactions produce short-range ferromagnetic correlations which persist up to room temperature. However magnetic saturation cannot be achieved for any of the alloys in applied fields of up to 180 kOe, indicating that strong negative interactions are also present.