Mattis’ Magnetics and Disordered Systems

Abstract

For non-ordered Fe alloys with concentration x>45 at.% of Al and x_Sn>50 at.% of Sn the dependence of magnetic parameters on the concentration, temperature and applied magnetic field are not characteristic of ferromagnets. Data [1-4] on the magnetic behavior of thin amorphous Fe-Sn films, being the closest in properties to the disordered nanocrystalline alloys, indicates that at x_Sn> 60 at.% Sn the ground magnetic state is of spin glass (SG), and in the interval of x=55-60 at.% Sn one may assume the coexistence of ferromagnetism (F) and SG. As far as the Fe-Al system is concerned, it is impossible to draw a conclusion on the peculiarities of the magnetic structure of higher AI concentration disordered alloys from magnetic measurements data alone where only the average magnetic moment per Fe atom [5,6] is registered. The magnetic state [7] of the disordered Fe₆₀AU₄₀ alloy was also determined as spin-glass. A considerable difference in the metalloid concentration of the vanishing average magnetic moment and the average hyperfine field, and the failure of saturation in the magnetization curves in the high external magnetic fields up to 5T (for Fe-Al alloys according to [6] even up to 15 T) can be regarded as the experimental signs of non-ferromagnetic behavior in high- concentration Fe-AI and Fe-Sn alloys. Concurrently, for these alloys there are no observed conventional signs for the spin-glass state such as the shifted about H_appl=0 hysteresis loop or true temperature hysteresis in the magnetization curves. Thus, the magnetic structure of disordered nanocrystalline Fe alloys with Al and Sn needs to be specified.