Surprising size-confinement effect of magnetocaloric materials

Scientists found that size-confinement - going from macroscopic bulk samples towards nanoparticles - leads to drastic changes in the atomic structure of certain magnetocaloric materials: The change from positive thermal expansion at the macroscale towards a negative thermal expansion (NTE) at the nanoscale. NTE materials are of increasing technological interest mostly because of the idea of mixing them with a symmetric negative thermal expansion material in order to create a composite material which has near-zero thermal expansion. The nanoparticle shape is particularly suitable for the design of such composites.