Enhanced magnetic anisotropy in (Fe0.7-xCo0.3Zrx)2 B nanocrystallites

Transition metal borides with a tetragonal structure are emerging as a strong candidate for rare-earth-free permanent magnet applications due to their inherently high magnetization, magnetocrystalline anisotropy, and Curie temperature. In this study, we developed (Fe0.7-xCo0.3Zrx)2 B (x = 0, 0.01, 0.02, 0.03, and 0.04) hard magnetic phase through arc melting followed by rapid solidification using melt spinning. X-ray diffraction (XRD) confirms the formation of a single phase tetragonal structure, with an average crystallite size in the range of ∼30-40 nm. Singular point detection (SPD) measurement showed that Zr incorporation enhances magnetocrystalline anisotropy, increasing the anisotropy field (Ha) from 7.5 to 9.5 kOe with an increase of Zr content from x = 0 to x = 0.03. Room-temperature magnetization loops reveal saturation magnetization (Ms) of 139–144 emu/g and an optimum coercivity of approximately 0.39 kOe. Additionally, Bloch’s law fitting of temperature-dependent saturation magnetization data suggests weakened ferromagnetic exchange interactions with increasing Zr content. These findings demonstrate that minor Zr incorporation significantly improves magnetic anisotropy, suggesting (Fe0.7Co0.3)2B-based alloys as promising candidates for next-generation, high-performance permanent magnets.