Effect of Annealing Temperature on Microstructure and Magnetocaloric Properties of Gd-Based Metallic Microfibers

In this paper, vacuum annealing has been adopted to introduce atomic cluster micro-regions inside Gd-based metallic microfibers to further explore the effect of the structural changes on the magnetocaloric properties and the mechanism which is systematically expressed. The experimental results indicate that the as-prepared Gd-based metallic microfibers have favorable amorphous formation ability and thermal stability. After annealing @ 380 °C, the maximum magnetic entropy change −ΔSmmax, refrigerating capacity (RC), and relative cooling power (RCP) values of the Gd-based metallic microfibers are 7.20 J/kg·K, 459.4 J/kg, and 588.7 J/kg, respectively. Combined with the transmission electron microscopy analysis results, the internal organizational order of the annealed microfibers is significantly altered, and the atomic clusters formed in localized regions, which reduce the magnetocrystalline anisotropy of the microfibers. While under the uni-action of an external magnetic field, the magnetic moment rotation state and magnetic domain structure distribution of the micro-region atoms will be changed obviously, thereby changing the general magnetic properties and magnetocaloric properties of the metallic microfibers. The above research results can promote the engineering application of Gd-based metallic microfibers in the field of magnetic refrigeration.