MnP Films with Desired Magnetic, Magnetocaloric, and Thermoelectric Properties for a Perspective Magneto-Thermo-Electric Cooling Device

A new magneto-thermo-electric cooling device (MTECD) comprising a central magnetocaloric (MC) material (e.g., Gd) sandwiched by two thermoelectric (TE) materials (e.g., MnP) is proposed. The presence of the TE materials in the MTECD guides the heat flow direction and enhances heat pulsation. In this case, the usage of a ferromagnetic TE material that combines large TE with small MC properties within a similar temperature region can enhance the magnetic flux density and heat exchange efficiency. Herein, it is shown that MnP nanorod-structured films with desired magnetic, MC, and TE properties are very promising for use in MTECDs. The films are grown on Si substrates at 300, 400, and 500 °C using molecular beam epitaxy. The 400 °C sample shows a desired TE and MC combination. A large power factor of 24.06 μW m⁻¹ K⁻² is achieved at room temperature. In this temperature region, the film exhibits a small MC effect (−ΔS_M ≈0.64 J kg⁻¹ K and ΔT_ad ≈0.3 K at μ₀H = 2 T) but ferromagnetism that gives rise to the enhanced MC effect of the central MC material. These properties can enable the MTECD to operate at high frequency.