Local structure of giant magnetocaloric system (Mn,Fe)₂(P,Si)

(Mn,Fe)₂(P,Si) is a promising system for magnetocaloric applications, with a tunable magnetostructural transition that ranges from about 320 K to 200 K, depending on the precise composition. As with other giant magnetocaloric systems with first-order magnetostructural transitions, the local interactions between neighboring atoms and magnetic moments are of crucial importance for the behavior of the system. To probe the local structure of (Mn,Fe)2(P,Si), we have conducted pair distribution function (PDF) analysis of x-ray and neutron total scattering data collected from powder samples with a range of Mn:Fe ratios, including measurements with an in situ magnetic field. A significant rearrangement of the local atomic structure is observed as a function of temperature and applied magnetic field. We present an analysis of the local atomic structure of these compounds and discuss the relevance to the observed magnetocaloric properties.