Tunable magnetocaloric effect around room temperature by Fe doping in Mn0.98Cr(0.02-x)FexAs compound

In this work, we present an investigation of the magnetic and magnetocaloric properties of MnCrFeAs compounds with x = 0.002, 0.005 and 0.010. Our findings show that as Fe content increases the unit cell volume decreases, which indicates that Fe doping emulates the pressure effect on the crystalline structure. The transition temperature T decreases as x increases and it can be set at approximate value of room temperature by changing the doping level. In addition, the magnetic entropy change ΔS was determined using a discontinuous measurement protocol, and realistic values from the magnetocaloric effect presented by MnAs-type compounds under pressure (emulated pressure) could be obtained. The values of ΔS are very large, around −11 JkgK with ΔH = 15 kOe, which is higher than that observed for most compounds with T around room temperature. However, ΔS is confined to a narrow temperature range of 11 K. To overcome this drawback, the composition of a theoretical composite formed by our samples was calculated in order to obtain a table-shaped ΔS curve. The simulated composite showed a high value of full width at half maximum δT of 33 K, which is much higher than that of single sample.
We acknowledge FAPERJ (Grant Nos. E-26/110.393/2014 and E-16/210.263/2014), CAPES, CNPq (Grant No. 485200/2013-9), FAPESP (Grant No. 2012/03480-0), PROPPI-UFF, MINECO and EU FEDER (project MAT2013-45165-P) and the PAI of the Regional Government of Andalucía for financial support.