Low Temperature Magnetic Behavior of Ni-Fe-Al-B Shape Memory Alloys: Magnetic Susceptibility and Mössbauer Spectra.

Abstract

AbstractMagnetic susceptibility measurements and Mössbauer spectra (MS) were performed on a series of NixFeyAlzB shape memory ribbons obtained by a melt spinning technique. The MS at room temperature show quadrupole splittings of two iron sites. At low temperatures (T<120 K) relaxed magnetic spectra begin to develop and, in one of the samples, a complete resolved magnetic spectrum at 13 K was observed. The overall magnetic susceptibility curves show non Curie-Weiss type behavior with peaks at around 60 K and 35 K. These curves also show magnetic hysteresis in the up-down temperature cycle used during the measurements. We relate our observations with a structural change occurring at temperatures between room temperature and 260 K, a second one around 200 K, and with the developing of spin-glass behavior at low temperatures, when the magnetic influences of Fe and Ni atoms almost compensate each other.