Enhanced ferromagnetism and microwave dielectric properties of Bi _0.95Y_0.05FeO₃ nanocrystals

Bi_0.95Y_0.05FeO₃ nanocrystals are synthesized by a hydrothermal method, and are crystallized in a rhombohedrally distorted perovskite BiFeO₃ structure in the R3c space, with compressive lattice distortion induced by the Y substitution at Bi sites from XRD study. Compared with BiFeO₃ gained under similar conditions, the magnetic properties are greatly enhanced, with saturate magnetization of 2.3emu/g at room temperature. Microwave dielectric properties of Bi _0.95Y_0.05FeO₃ nanocrystals are investigated in the range of 2-18 GHz. The Y substitution results in the increase of permeability and decrease of permittivity, which are attributed to the enhanced spin relaxation of domain wall motion and the weakened electron-relaxation caused by decreasing Fe²⁺, respectively. The changes for microwave dielectric response could lead to the excellent microwave absorption due to the improvement of the impedance match between BiFeO₃ and air.