Size dependence of magnetic and dielectric properties in YCr0.5Fe0.5O3 ceramics

The YCr0.5Fe0.5O3 ceramics with different sintering temperatures (T-s) have been synthesized by a sol-gel method, and the structural, magnetic and dielectric properties are studied. With the decrease of T-s, continuous decrease of grain size is evidenced via the micromorphology analysis. Due to the competition between the single ion magnetic anisotropy and the antisymmetric Dzyaloshinsky-Moriya interaction, the total magnetization becomes zero at the compensation temperature (T-comp) in the presence of a lower magnetic field, and the T-comp exhibits size dependent behavior. With the decrease of grain size, the T-comp becomes lower due to the increase of uncompensated spins. Meanwhile, the T-comp is adjustable by the magnetic field, and a larger external field drives the Tcomp to lower temperature. After cooling the samples in magnetic field, the magnetic anisotropy is established, which results in a positive exchange bias (EB) effect below the T-comp. The decrease of T-s would increase the ferromagnetic component, which leads to the decrease of EB field (H-EB). The dielectric measurements suggest that the samples of T-s = 900 and 800 degrees C possess large permittivity accompanied with dielectric relaxation near room temperature, and the dielectric relaxation which arises from the single-ionized oxygen vacancies moves to higher temperature with the decrease of T-s.