Magnetocaloric effect in Fe–Cr–Cu–Nb–Si–B amorphous materials

Abstract

Amorphous soft magnetic Fe 78− x Cr x Cu 1Nb 5Si 4B 12 ribbons ( x = 0, 5 and 8) have been fabricated by melt-spinning technique. The value of magnetocaloric effect has been determined from the measurements of magnetization as a function of temperature and an external magnetic field. With the increase in Cr content in the alloy, the value of the entropy change decreases, and at the same time, the Curie temperature also decreases. From the functional point of view, the material to be used for magnetic refrigeration should be characterised by the greatest possible entropy change near room temperature. The alloy containing 8 at.% Cr, whose Curie temperature is 285 K and the entropy change reaches 1 J/kg K at the magnetic field of 20 kOe, is closest to meeting this condition. The critical behaviour of this alloy in the amorphous state has been studied near its Curie temperature. From the values of the critical exponents ( β = 0.31 ± 0.02 and γ = 1.60 ± 0.02) it can be concluded that the alloy behaves like 3D Heisenberg ferromagnet in an amorphous state. The results from this work showed that Cr-containing amorphous alloy with 8 at.% Cr is an interesting material and potential candidate for magnetic refrigerants working near room temperature.