Sm-Doped NiO Nanoparticles for Magnetic Memory at Room Temperature

The search for diluted magnetic semiconductors (DMSs) has gained immense research interest because of the coexistence of the charge and spin degree of freedom in a single substance to realize a particular class of spintronic devices, and a rare earth (RE)-doped transition-metal oxide (TMO) is one of the choices. This study intends to understand the effect of RE Sm3+ ion substitution in antiferromagnetic (AF) NiO nanoparticles (NPs) using modern cutting-edge techniques (synchrotron powder X-ray diffraction and soft X-ray absorption, Raman scattering, and superconducting quantum interference device magnetometry). A percolation threshold limit of about 1% incorporation of Sm3+ ions at the Ni2+ site was evident. An enhanced magnetic moment observed for an intermediate composition has been attributed to the interacting bound magnetic polaron. A core–shell model has been proposed such that the multivalent point defects reside at the surface of NPs, whereas the core of the particles retains AF properties. The exchange coupling mediated by interfacial frozen spins is the leading mechanism behind the magnetic memory effect at room temperature. The outcome of this study is vital for the future development of RE-functionalized TMO DMS spintronic devices and the understanding of their fundamental physics and chemistry.