A combined study on microstructure, microchemistry and magnetic behavior of (Sm_0.12Co_0.88)₉₅Hf₁B₄ nano-composite ribbons by electron microscopy and atom probe tomography

In this work, Hf and B modified ribbon produced by RSP (rapid solidification process) method have been studied to investigate the microstructure, phase formation and magnetic properties of the Sm-Co-based alloy. (Sm_0.12Co_0.88)₉₅Hf₁B₄ ribbon has been synthesized and annealed at various temperatures (700 °C, 800 °C & 900 °C) to analyze the effect of temperature on magnetic properties and structure. X-ray diffraction (XRD) phase analysis has confirmed the 1:7 H phase as a significant phase in the as-spun ribbon. A combination of 1:5 H and 2:17 R phases were found in the ribbon annealed at 900 °C due to disorder-order transformation upon heat treatment. The development of ordered structure and grain growth upon annealing at 800 °C and 900 °C have deteriorated the magnetic properties. Scanning electron microscopy (SEM) and Transmission electron microscopy (TEM) analysis also revealed the grain growth and the development of the ordered 2:17 R structure upon annealing. The ribbon annealed at 700 °C showed better magnetic properties, H_c≈ 8.6 kOe, M_r ≈ 49 emu/g and (BH)_max≈ 5.63 MGOe with an average grain size of ∼149 ± 5 nm. T_C of the as-spun ribbon was found to be ⁓750 °C, and the temperature co-efficient of magnetization (α) and coercivity (β) were about − 0.008 and − 0.161%/°C, respectively. The APT analysis confirmed the fine borides in both as-spun and annealed (700 °C & 900 °C) ribbons.