Effects of Cu doping on the magnetism of CeO 2 nanoparticles

Abstract

Magnetic properties of 5.5 nm Cu xCe 1-xO 2 nanoparticles (NPs) with change in Cu doping (x = 0, 2.5, 5.0, 7.5, and 10%) are investigated to examine the controversial issue of room temperature ferromagnetism (FM) in this system. The data of magnetization M versus magnetic field H fit the equation: M M fpH with M f (X p) being the FM (paramagnetic) part. The observed FM saturation magnetization M S 8.5 10 -5emu/g for x = 0 is suggested to be due to Fe impurities detected in the samples at 20 ppm level. However, in the doped samples, both X p and M S increase nearly linearly with x with the FM magnetic moment μ S ≈ 3 10 -4μ B/Cu atom. This magnitude of S, although considerably smaller than S ≈ 1 B/Cu atom reported in thin films of Cu xCe 1-xO 2, is argued to be an intrinsic effect due to Cu doping. Electron magnetic resonance studies show lines due to Cu 2+ ions in the doped samples. © 2012 American Institute of Physics.