Quantum Materials - 03

Abstract

NdFeB magnets are important materials which are used in motors, electrical appliances, etc. [1]. The coercivity of the magnets is often reinforced by adding dysprosium (Dy) for practical usage. The formation of Dy-rich shells, (Nd_1-xDy_x)₂Fe₁₄B, is considered important for the reinforcement of the coercivity [2] and understanding their magnetic properties is an important subject. In this work, we study the magnetic properties of (Nd_1-xDy_x)₂Fe₁₄B with random Dy-substitution using a recently developed atomistic model [3,4]. We focus on the field dependence of the magnetization along the easy [001] and hard [100] axes for a range of Dy concentration (x =0.0, 0.2, 0.4, 0.5, 0.6, 0.8, 1.0). Our model, with microscopic parameters derived primarily from first-principles calculations [4], quantifies the concentration x-dependence of the saturation magnetization (M_sat), anisotropy field (H_a), and the anisotropy constant (K₁). Furthermore, we analyze the spin-canting angles to elucidate the mechanism behind the decrease in saturation magnetization. We discuss the detailed features of their quantities. Our computational results provide insights into the structure-property relationship essential for tailoring the magnetic performance of NdFeB magnetic through compositional control.