Self-Assembly and Enhanced Magnetic Properties of Three-Dimensional Superlattice Structures Composed of Cube-Shaped EuS Nanocrystals

Superlattice structures (SLSs) assembled with cube-shaped EuS nanocrystals (NCs) and their remarkable magnetic properties are reported. The cube-shaped EuS NCs are prepared by the thermal reduction of single source precursor, tetra(diethyldithiocarbamate) europium complex with oleylamine as a surface modified regent. The fine structures of the three-dimensional (3D) SLSs assembled with EuS NCs are characterized by TEM, small-angle XRD, and electron transmission tomographic analysis. Magnetic measurements of the SLSs on polymer films with SQUID show that the coercive field of the SLSs assembled with cube-shaped EuS NCs are twice larger than those of cube-shaped EuS NCs powder. The enhanced magnetic properties are attributed to magnetic dipole interaction between cube-shaped EuS NCs in SLS structures.