A Mössbauer spectroscopy study of the structural and magnetic properties of Nd16(Fe0.78Co0.18Mo0.04)76B8 and Nd16(Fe0.80Co0.18W0.02)76B8

Abstract

The crystallographic and magnetic properties of Nd16(Fe0.78Co0.18Wo0.02)76B8 and Nd16(Fe0.80Co0.18W0.02)76B8, for the sake of contrast analysis, including Nd16(Fe0.82Co0.18)76B8 and Nd16Fe76B8, have been investigated by a Mössbauer effect study with six magnetic Lorentzian sextets and one paramagnetic Lorentzian doublet at room temperature. The hyperfine field changes with the addition of transition-metal molybdenum or tungsten into Nd16(Fe0.82Co0.18)76B8 indicating a preferential occupation of the k2, {e,c} sites for molybdenum atoms and of the j1, k2, and e sites for the tungsten atoms over the six distinct iron sites in the tetragonal phases of these magnetic alloys. The Mössbauer spectral analysis confirms that the transition metals molybdenum and tungsten characterize Nd16(Fe0.78Co0.18Mo0.04)76B8 and Nd16(Fe0.80Co0.18W0.02)76B8 in coercivities, Curie temperatures, and saturation magnetizations, and even in the stabilities of the alloys. The microscopic structure of the paramagnetic phases in these alloys, which is non-negligible in determining the performance of the magnetic alloys, is otherwise shown to be modified by substitution of these transition metals for iron based on the present Mössbauer spectral study.