Direct measurement of the magnetocaloric effect in MnFe(P,X)(X= As, Ge, Si) materials

An investigation of the magnetocaloric effect (MCE) displayed by three generations of MnFe(P,X) (X = As, Ge, Si) materials has been carried out by combining indirect ΔS and direct ΔTad measurements. To be able to compare the performances of the new Si-based system with the already well-known As- and Ge-based materials in optimal conditions, both the Mn/Fe and P/Si ratios of the MnxFe1.95−xP1−ySiy compounds were optimized to display the largest MCE around room temperature. Here, we show that the maximum values of ΔTad (ΔB = 1.1 T) and ΔS (ΔB = 1 T) are respectively ∼2.2 K and ∼8 J kg−1 K−1 in the Si-based material Mn1.25Fe0.7P0.49Si0.51. These values are very close to the MCE performances of the As-based and Ge-based compounds. A critical comparison of these three MnFe(P,X) series highlights the role played by the non-magnetic elements on the latent heat at the Curie temperature. The combination of: (i) large ΔS and ΔTad in intermediate magnetic fields, (ii) limited thermal/magnetic hysteresis, (iii) easy tunability of the Curie temperatures and (iv) practical advantages like cheap, non-critical and non-toxic starting materials; makes the MnxFe1.95−xP1−ySiy family highly promising for magnetic refrigeration applications.