Magnetic and structural properties of nanocomposite permanent magnet produced from crystallization of Pr4Fe67Nb4Cu2Zr1B22 alloy

Present research work narrates synthesis, structural, thermal and magnetic characteristics of Pr ₄Fe ₆₇Nb ₄Cu ₂Zr ₁B ₂₂ nanocomposite magnets. Amorphous Pr ₄Fe ₆₇Nb ₄Cu ₂Zr ₁B ₂₂ rods were produced through injection casting technique and permanent magnetic characteristics were obtained by one-step annealing the amorphous rods. XRD analysis elucidated that as-cast rods have amorphous phase structure and annealed magnets have tetragonal Pr ₂Fe ₁₄B hard phase, cubic structural α-Fe phase and tetragonal Fe ₃B soft phase. Optimal annealed magnet composed of 63% Pr ₂Fe ₁₄B hard phase, 26% α-Fe and 11% Fe ₃B soft phases with mean grain sizes around 51.6 ± 1 nm for Pr ₂Fe ₁₄B, 25.4 ± 2 nm for α-Fe and 21.5 ± 2 nm for Fe ₃B phases. Microscopic and atomic probe studies showed that the annealed magnet consists of Pr ₂Fe ₁₄B, α-Fe, Fe ₃B nanosized grains interlinked with thin grain boundaries. Henkel curve evidenced the existence of inter-grain exchange coupling between magnetic nanophase grains. Magnetic hysteresis measurements revealed that Pr ₄Fe ₆₇Nb ₄Cu ₂Zr ₁B ₂₂ nanocomposite magnet yielded maximum magnetic characteristics such as coercivity H _c of 382 kA/m, remanence B _r of 0.70 T and maximum energy product ( BH) _max of 64.2 kJ/m ³ with rare earth to iron ratio 4:67.