Effect of replacing RE and TM on magnetic properties and thermal stability of some Al-Ni-based amorphous alloys

Abstract

Amorphous ribbons Al86Ni8Ho6, Al86Ni8Gd6 and Al86Ni6Co2Gd4Y2 were prepared by quenching from 1580-1600 K using spinning technique at a wheel speed of 32 m/s. X-ray diffraction (XRD) analysis of the quenched alloys revealed a clear prepeak located below the main amorphous peak. The specimens crystallize in three stages but glass transition temperature was not found. The crystalinity was calculated by both XRD and differential scanning calorimetry (DSC) methods for all samples. Magnetic properties of ribbons were investigated in wide ranges of temperature (T = 4-900 K) and magnetic field (up to 30 kOe) by Faraday method and vibration sample magnetometry (VSM). The amorphous alloys investigated have no magnetic ordering at low temperatures down to T = 4 K but demonstrate the superparamagnetic behavior. The magnetic properties are discussed in the frames of conception of existence the superparamagnetic clusters with ferrimagnetic ordering. (C) 2012 Elsevier B. V. All rights reserved.