The role of Mn in the stabilization of adiabatic temperature changes of LaFe _{11.2− <i>x</i>} Mn _<i>x</i> Co _0.7 Si _1.1 alloys in an alternating magnetic field

Abstract The results of the study of the effect of partial substitution of Fe by Mn in the LaFe 11.2− x Mn x Co 0.7 Si 1.1 system on magnetization, specific heat, magnetostriction and magnetocaloric effect are presented. Direct measurements of the adiabatic temperature change (∆ T ad ) were carried out in alternating magnetic fields (AMF) using the magnetic field modulation method. Partial substitution of Fe atoms by Mn atoms leads to a shift in the Curie temperature ( T C ) towards lower temperatures without a noticeable deterioration in magnetic properties. A correlation was found between the structural component of the magnetocaloric effect and the stability of the frequency of the ∆ T ad in the AMFs—an increase in the manganese concentration leads to a decrease in magnetostriction and to a lower dependence of ∆ T ad on the frequency of the magnetic field. Estimates of the specific cooling power Q C as a function of the frequency of the AMF showed that the highest value of Q C at f = 20 Hz in a magnetic field of 12 kOe is 26.3 W g −1 and is observed for the composition with x = 0.1. This value is higher than that of Gd, for which, under the same conditions, Q C = 21.6 W g −1 . All the samples studied show stability of the value of Δ T ad without any sign of deterioration of the effect up to 60,000 cycles of switching on/off of the magnetic field of 12 kOe. The discovered frequency and cyclic stability of ΔT ad of the studied samples increase their prospects for application in magnetic cooling technology.