Magnetism of nanocrystalline and bulk fexNi23-xB6 (x=0, 1, 22 and 23) alloys -- experiment and theory

Formation of the nanostructure composed of a metastable magnetically ordered fcc-FexNi23-xB6 phase with large lattice constant (a=1.051-1.082 nm) from amorphous Fe81-y-zNiyZr7B12Auy (y=10-40, 64; z=0, 1) precursors due to the thermal treatment have been studied. Annealing of the y<=20, z=0 samples at temperatures 420-580°C leads to the increase of FexNi23-xB6 fraction embedded in amorphous matrix with grains sizes from few to few dozen nanometres. The structure transformations have been investigated by the DSC, XRD and TEM techniques. Magnetic behaviour of FexNi23-xB6 (x=0, 1, 22 and 23) phases have been studied theoretically using the spin polarized tight binding linear muffintin orbital (TB-LMTO) method. Anomalously high magnetic moments of Fe atoms have been found in some non-equivalent positions in the crystal structure.