MnxFe5_ xSi3 for active magnetic regenerative refrigeration at room temperature

Abstract

Magnetocaloric properties of MnxFe5_xSi3 with x = 1, 1.1, 1.2, 1.3 were investigated for use in an active magnetic regenerator (AMR) for room temperature refrigeration. The Mn content was adjusted to tailor their Curie temperature and, hence, the operating range of the magnetic refrigerant. The peak magnetic entropy change and the maximum adiabatic temperature change for MnxFe5_xSi3 decreased with increasing Mn substitution. An in-house AMR testbed was built to investigate the suitability of the refrigerant in an AMR cycle. The maximum temperature span between cold and hot ends achieved by the AMR testbed using Mn1.2Fe3.8Si3 was 4.75 K at 300 K compared to 7.5 K for Gd. It was also demonstrated that the morphology of the refrigerant can have a measurable effect on the heat exchange between the refrigerant and the cooling fluid, which highlights that designing a solid magnetic refrigerant also requires appropriate technology to process the material to the desired size and shape. The magnetic refrigerant characteristics of MnxFe5_xSi3 were substantially inferior to those of Gd, but MnxFe5_xSi3 remains attractive in terms of material cost and processability.