Signature of multiferroicity and impedance analysis of Co1−xZnxFe2−xLaxO4 nanoparticles

Abstract

Effects of Zn2+/La3+ co-doping on multiferroic and impedance properties of co-precipitation derived Co1−xZnxFe2−xLaxO4 (x = 0.0, 0.1 and 0.3) nanoparticles have been investigated. The powder X-ray diffraction study confirms the pure phase, cubic spinal structure and particle size varies between 20 and 22 nm. The particle size decreases with increase in co-substitution indicating the short range ordering in CoFe2O4. The relaxations in dielectric constant follow Maxwell–Wagner polarization and arise out of charge transfer of Co and Fe ions in multi-oxidation states. The co-substitution of Zn2+/La3+ in CoFe2O4 at A and B sites respectively results in improvement of Nquist plot and impedance of the nanoparticle which confirms space charge polarization caused by piling of charges at the interface of grain and grain boundries. An unusual relaxation behavior is also observed in co-substituted CoFe2O4 which may be useful in enhancing the multiferroic properties at room temperature. It could be noted the GBs are more resistive as compared to the grains, resulting in high impedance value and non-Debye type behavior in the Co1−xZnxFe2−xLaxO4 nano particles. Low and stable coercivity (Hc) of 393.13 Oe have been observed and a stable saturation magnetization has been achieved at room temperature. P–E loops have rounded corners which may be the due to the aggregation of CoFe2O4 nanoparticles with each other resulting out of their strong magnetization. Simultaneous occurrence of saturation magnetization and weak ferroelectricity (P–E loop) with high values of impedance and dielectric constant confirm the signature of multiferroicity in Co1−xZnxFe2−xLaxO4 nanoparticles.