First-order-reversal-curve analysis of rare earth permanent magnet nanostructures: insight into the coercivity enhancement mechanism through regulating the Nd-rich phase

Abstract

Rare earth permanent magnet nanostructures have attracted intensive interest recently due to the increasing demand for integrated and miniaturized devices. As a typical example, hard magnetic Nd₂Fe₁₄B-based nanostructures with desired coercivity have been developed by a reduction–diffusion process and the Nd-rich phase is supposed to be essential to optimize the magnetic properties, whereas the identification and role of the Nd-rich phase have not been addressed so far. Herein, Nd₂Fe₁₄B-based nanostructures with different Nd-rich phase contents, Nd₁₅Fe₇₇B₈ and Nd_14.2Fe_78.6B_7.2, are rationally prepared by a reduction–diffusion process. The coercivity of Nd₁₅Fe₇₇B₈ can reach 5 kOe, which is higher than that of Nd_14.2Fe_78.6B_7.2 of 3.2 kOe. First-order-reversal-curve (FORC) analysis confirms the amorphous paramagnetic Nd-rich phase as pinning centers and reveals magnetic interactions and magnetic domain nature in the two nanostructures. The increase of the Nd-rich phase optimizes microstructures and magnetic interactions, responsible for higher coercivity. This work points out the relationship between the Nd-rich phase, magnetic interactions, microstructures, and magnetic properties, and could usher in new ways of fabricating advanced permanent magnetic nanostructures.