Critical magnetic and magnetocaloric behavior of amorphous melt-extracted Gd50(Co69.25Fe4.25Si13B13.5)50 microwires

Abstract

We report on the structural, magnetic, and magnetocaloric properties and critical behavior of high-quality amorphous melt-extracted Gd50(Co69.25Fe4.25Si13B13.5)50 alloy microwires with an average diameter of 42 μm. The microwires undergo a second-order paramagnetic to ferromagnetic (PM-FM) transition around the Curie temperature, TC ∼ 174 K. Around the PM-FM phase transition temperature, the magnetic entropy change ΔSM reaches a maximum value ΔSMmax of about 5.9 J/kg K for a magnetic field change of 5 T. An iterative Kouvel-Fisher method was used to analyze the critical behavior of the second-order phase transition. The critical exponent values are β = 0.493 ± 0.005, γ = 1.321 ± 0.011, and δ = 3.678 ± 0.073, which are close to those expected for the mean-field model with long-range interactions below TC and for the 3D-Heisenberg model with short-range interactions above TC. The magnetic and magnetocaloric behaviors of the Gd alloy microwires near the PM-FM phase transition are discussed.