Synthesis, structural and magnetic properties of the nanocomposite Fe ₆₃B ₂₃Nd ₇Y ₃Nb ₃Cr ₁ magnets

The Fe ₆₃B ₂₃Nd ₇Y ₃Nb ₃Cr ₁ nanocomposite magnets in the form of sheets have been prepared by copper mold casting technique. The phase evolution, crystal structure, microstructural and magnetic properties have been investigated in the as-cast and annealed states. The as-cast sheets show magnetically soft behaviors which become magnetically hard by thermal annealing. The optimal annealed microstructure was composed of nanosize soft magnetic α-Fe (1929 nm) and hard magnetic Nd ₂Fe ₁₄B (4555 nm) grains. The best hard magnetic properties such as intrinsic coercivity, _jH _c of 1119 kA/m, remanence, B _r of 0.44 T, magnetic induction to saturation magnetization ratio, M _r/M _s=0.61 and maximum energy product, (BH) _max of 55 kJ/m ³ was obtained after annealing at 680 °C for 15 min. The annealing treatment above 680 °C results in non-ideal phase grains growth, which degrade the magnetic properties.