Low-temperature magnetic susceptibility of Fe-B amorphous alloys (abstract)

Abstract

Magnetic properties of amorphous iron based alloys have been extensively studied, however, the mechanism of thermal demagnetization is not well understood and temperature dependence of the static magnetic susceptibility is not well known. In order to address some of these problems we performed an accurate magnetization study of Fe100−xBx metallic glasses (x=20,18,16,14) at low temperatures (4.2–160 K) and in several magnetic fields up to 15 kOe. Magnetization measurements were carried out using VSM with an accuracy of 10−4. At a fixed temperature, the magnetization was measured as a function of an external magnetic field. The demagnetization field was subtracted and the saturation magnetization was determined by linear extrapolation to zero internal field. The saturation susceptibility was obtained from the slope of this curve. The temperature dependence of the saturation magnetization is best described by a T3/2 term, however, the saturation susceptibility is a nonmonotonous function of temperature and cannot be described by spin wave contribution. It exhibits a minimum at low temperature suggesting that some atoms are in zero effective internal fields induced by the mixture of ferro- and antiferromagnetic interactions. The temperature of the susceptibility minimum is lower for higher iron concentration in the alloys. The influence of magnetovolume effects on experimental data is addressed and the results are discussed in terms of inhomogeneous magnetic order.