Magnetic superlattices and their nanoscale phase transition effects

The systematic assembly of nanoscale constituents into highly ordered superlattices is of significant interest because of the potential of their multifunctionalities and the discovery of new collective properties. However, Successful observations of such superlattice-associated nanoscale phenomena are still elusive. Here, we present magnetic superlattices of Co and Fe3O4 nanoparticles with multidimensional symmetry of either AB (NaCl) or AB(2) (AlB2). The discovery of significant enhancement (approximate to 25 times) of ferrimagnetism is further revealed by forming previously undescribed superlattices of magnetically soft-hard Fe3O4@COFe2O4 through the confined geometrical effect of thermally driven intrasuperlattice phase transition between the nanoparticulate components.