Intragranular strain scanning 3DXRD experiments on the ferromagnetic phase transition in (Mn,Fe)2(P,Si) magnetocaloric compounds

In the high-performance and low-cost (Mn,Fe)2(P,Si) magnetocaloric compounds the ferromagnetic phase transition is accompanied by latent heat. The transition temperature TC can be conveniently tuned around room temperature by changing the Mn/Fe and P/Si ratios. This system is a very promising candidate for magnetic cooling and power conversion applications. A key limitation for the application of these materials is their brittle mechanical properties that potentially limit their cycle life during the operational thermo-magnetic cycling. At TC the hexagonal unit cell shows a sizeable change in the c/a ratio of the lattice parameters, resulting in significant shear stresses near the ferromagnetic (FM)/paramagnetic (PM) interfaces at TC. Intragranular orientation and strain scanning 3DXRD experiments will provide a unique insight in the local strains near the FM/PM interfaces in both single-crystalline and poly-crystalline samples during thermal and magnetic field scans.