Structural and Magnetic Properties of Sm(Co0.7Fe0.1Ni0.12Zr0.04B0.04)7.5 Melt Spun Isotropic and Anisotropic Ribbons

TL;DR

This study investigates the structural and magnetic properties of Sm-Co-Fe-Ni-Zr-B melt-spun ribbons, revealing phase transformations, nanocrystalline microstructure, high coercivity, and energy product improvements, especially in anisotropic samples.

Contribution

It provides new insights into phase evolution, microstructure, and magnetic performance of melt-spun Sm-based ribbons with various compositions and processing conditions.

Findings

Hexagonal SmCo7 structure identified in as-spun ribbons

High coercivity values up to 27 kOe achieved

Maximum energy product of 12 MGOe in anisotropic ribbons

Abstract

We have investigated the structural and magnetic properties of Sm(Co0.7Fe0.1Ni0.12Zr0.04B0.04)7.5 melt spun ribbons. Samples were arc melted then melt spun at 37 m/s up to 55 m/s to obtain ribbon for powdering. Annealing has been performed in argon atmosphere for (30 to 75) min at (600 to 870) oC. In as-spun ribbons the hexagonal SmCo7 (TbCu7-type of structure) of crystal structure has been determined from x-ray diffraction patterns, while fcc-Co has been identified as a secondary phase. After annealing, the 1:7 phase of the as-spun ribbons transforms into 2:17 and 1:5 phases. X-ray patterns for as-milled powders exhibit very broad peaks making it difficult to identify a precise structure but represent the 1:7 structure after annealing at low temperature (650 oC). TEM analysis shows a homogeneous nanocrystalline microstructure with average grain size of (30 to 80) nm. Coercivity values of (15 to 27) kOe are obtained from hysteresis loops traced up to a field of 5 T. The coercivity decreases as temperature increases, but it maintains values higher than 5 kOe at 380 oC. The maximum energy product at room temperature increases, as high as 7.2 MGOe, for melt-spun isotropic ribbons produced at higher wheel speeds. Anisotropic ribbons have a maximum energy product close to 12 MGOe.