Magnetic characterization of rare-earth oxide nanoparticles

High saturation magnetization and hysteresis-less magnetic responses are desirable for nanoparticles in scientific and technological applications. Rare-earth oxides are potentially promising materials because of their paramagnetism and high magnetic susceptibility in the bulk, but the magnetic properties of their nanoparticles remain incompletely characterized. Here, we present full M–H loops for commercial RE2O3 nanoparticles (RE = Er, Gd, Dy, Ho) with radii from 10–25 nm at room temperature and 4 K. The magnetic responses are consistent with two distinct populations of atoms, one displaying the ideal Re3+ magnetic moment and the other displaying a sub-ideal magnetic moment. If all sub-ideal ions are taken to be on the surface, the data are consistent with ≈ 2 − 10 nm surface layers of reduced magnetization. The magnetization of the rare-earth oxide nanoparticles at low temperatures (1.3–1.9 T) exceeds that of the best iron-based nanoparticles, making rare-earth oxides candidates for use in next-generation cryogenic magnetic devices that demand a combination of hysteresis-less response and high magnetization.