High Relative Cooling Power in a Multiphase Magnetocaloric FeNiB Alloy

Low-cost magnetic cooling based on the magnetocaloric effect is an energy efficient, environmentally friendly, thermal management technology. However, inadequate temperature span is often a challenge in developing a magnetic cooling system. We report the novel use of multiphase materials to enhance the working temperature span (δT_FWHM) of the magnetic entropy change and the relative cooling power of a Fe-Ni-B bulk alloy. The coexistence of bcc, fcc, and spinel phases results in large working temperature spans of 322.3 and 439.0 K for magnetic field change of 1 and 5 T, respectively. δT_FWHM for this multiphase (Fe₇₀Ni₃₀)₈₉B₁₁ alloy is about 86% higher than the corresponding value for single-phase γ-(Fe₇₀Ni₃₀)₈₉B₁₁ alloy for ΔH = 1 T. These values are the largest for any bulk magnetocaloric material and even higher than most magnetocaloric nanoparticles. The relative cooling power is also higher than comparable materials, including the benchmark magnetocaloric material, gadolinium.