Nano Scaled Checkerboards: A Long Range Ordering in NiCoMnAl Magnetic Shape Memory Alloy Thin Films with Martensitic Intercalations

Magnetic shape memory Heusler alloys, such as NiCoMnAl, are considered promising candidates for magnetocaloric cooling applications. Grown in thin film systems of adjacent layers with austenite and martensite crystal structures almost equal thicknesses, a long-range ordering phenomenon the 3D checkerboard pattern occurs NiCoMnAl samples. The crystallographic origin is proven by transmission electron microscopy (TEM) techniques. darker fields arrangement consist nuclei superposed austenite, while purely regions appear bright TEM cross sections. nucleation process presumably triggered inhomogeneous local elastic stray primary martensitic matrix limited thicknesses films.