Magnetism and phase structure of crystallized Sm–Fe–B melt spun ribbons

Abstract

The crystallization of amorphous SmxFe80−xB20 melt spunribbons is studied over an extended range of composition(0 < x < 8).Differential scanning calorimetry scans reveal different endo- and exothermic effectsdepending upon the composition. X-ray diffraction and Mössbauer studies for samplesannealed at temperatures close to the onset of the first exothermic effect provethat, during the primary crystallization of the amorphous ribbons, both α-Feand Fe3B phases appear—with Sm ions randomly accommodating the Fe sites inthe tetragonal Fe3B lattice—while the subsequent exothermic reactionscorrespond to the decomposition of the metastable Fe3B phase into α-Fe andFe2B and to the formation of the ternary Sm1.1Fe4B4 phase. Fully crystallized ribbonswith Sm contents lower than about 7 at.% show the co-existence between α-Feand Fe2B soft magnetic phases and the Sm2Fe14B magnetic one. Theenhancement of magnetic properties with increasing relative proportionof magnetic phase is discussed and correlated with exchange couplingand spin wave stiffness data obtained from the magnetic measurements.