Structural, Magnetic, and Positron Annihilation Characteristics of Zn and Zr-Substituted CuFe2O4 for Magnetic Temperature Controller

Abstract

The effects of Zr+4 and Zn+2 substitution on the structural, microstructural, and magnetic properties of Cu1−xZnxZryFe2−yO4 + δ ferrites prepared by a double-sintering ceramic technique have been investigated. From X-ray diffraction analysis, it was found that substitution of Zn and Zr enhanced simultaneously sintering process and crystallization. On the other hand, the initial permeability decreases sharply at Curie temperature for compositions, which make Zn/Zr-co-doped NiFe2O4 spinel ferrites a very promising candidate for magnetic switch, magnetic temperature transducer (MTT), and temperature-sensitive controller devices. The important change of Curie temperature of CuFe2O4 compound occurs by simply controlling the contents of Zn and Zr within CuFe2O4 and results in obtaining magnetic materials, with desired Curie temperature. Magnetic hysteresis loop measurements show that the magnetic moment increases by Zn and Zr substitution for the studied systems. The positron annihilation lifetime (PAL) measurements revealed that there are good correlations between PAL parameters (τ1, I1, τ2, and I2), porosity (P), and crystallite size (t) for the Cu1−xZnxZryFe2−yO4 + δ ferrite system. The line shape parameters S and W from the Doppler broadening measurements which describe the annihilations with valence and core electrons, respectively, are calculated. We find a systematic increase in the S and a decrease in the W parameter due to the increase of the size and/or the concentration of defect density caused by adding Zn and Zr ions. Correlations were also made between the PAL parameters and the initial magnetic permeability (μi), saturation magnetization (Ms), and the coercive field (Hc).