Systematic investigation of Mn substituted La(Fe,Si)13 alloys and their hydrides for room-temperature magnetocaloric application

Fully hydrogenated Mn containing LaFeSi alloys provide long time stability of attractive magnetocaloric properties; issues of previously reported induced phase co-existence can be avoided. In this paper, two series LaFe11.8 xSi1.2Mnx and LaFe11.6 xSi1.4Mnx (x = 0, 0.1, 0.2, 0.3, 0.4), before and after hydrogenation are presented. In the non-hydrogenated parent samples, microstructural evolution and phase formation with increasing Mn content are studied. It is found that materials combination within the sample series can provide constant MCE over a large working temperature range. As a peculiarity, the hydrogenated compounds show a different dependence of the transition temperature as a function of Si content than the parent compounds. This behaviour is explained by comparing the amount of hydrogen incorporated in samples with different Si content. Moreover, an estimation for the maximum adiabatic temperature change and optimal magnetic field is given exemplarily for a non-hydrogenated and a hydrogenated compound.