Thermomagnetic Analysis of Nanocrystalline Nd_4.5Fe₇₇B_18.5 Alloy

Abstract

Changes in the phase composition and crystallite size of a rapid quenched Nd_4.5Fe₇₇B_18.5 alloy, caused by thermomagnetic measurements (TM) have been studied using XRD methods of phase analysis, crystallite size and lattice microstrain determination. Structural changes in regard to optimal magnetic state were additionally analyzed by TEM. Magnetic properties in optimal magnetic state and after TM were observed using room temperature SQUID measurements. The obtained experimental results suggest the Fe₃B/Nd₂Fe₁₄B and partly α-Fe nanocomposite structure of the alloy in the optimized magnetic state, with mean crystallite size (<30 nm). After TM, an increased amount of α-Fe phase, presence of different oxide and Fe-B phases as well as growth of crystallites are found to be the main reasons for the observed quality loss of hard magnetic properties.