Defect characteristics, local electron density, and magnetic properties of rare Earth-doped CuFeO2 ceramics

Abstract

Polycrystalline CuFeO2 (CFO) and CuFe0.99R0.01O2 (R–CFO, R = La, Sm, Eu, Gd, Dy, and Ho) were prepared via solid-phase synthesis to investigate the effects of rare-earth (R) ion addition on the microstructures and magnetism. Positron annihilation lifetime spectroscopy (PALS) experimental results demonstrated that the size, concentration, and defect types were altered by R substitution due to the competition between the agglomeration of small-sized defects and the decomposition of vacancy clusters, which resulted in the redistribution of electrons around annihilation sites. The magnetic measurements revealed that the antiferromagnetic stability was influenced by R substitution, which was ascribed to the effect of magnetic moments, variations in exchange interactions, and the partial reduction of spin frustration. The magnetization behaviors of the R–CFO samples were also influenced by doping ions, which was mainly explained by the different magnitudes of the R ions’ magnetic moments. Ferromagnetism and antiferromagnetism were present in all of the samples. The local electron density ne was associated with the maximum magnetization (Mm). The correlative physical mechanisms are discussed in detail. The results demonstrated that the ne plays an important role in regulating the magnetic properties of CFO ceramics.