Temperature-Dependent Magnetic Response of Antiferromagnetic Doping in Cobalt Ferrite Nanostructures
In this work MnxCo1−xFe2O4 nanoparticles (NPs) were synthesized using a chemical co-precipitation method. Phase purity and structural analyses of synthesized NPs were performed by X-ray diffractometer (XRD). Transmission electron microscopy (TEM) reveals the presence of highly crystalline and narrowly-dispersed NPs with average diameter of 14 nm. The Fourier transform infrared (FTIR) spectrum was measured in the range of 400–4000 cm−1 which confirmed the formation of vibrational frequency bands associated with the entire spinel structure. Temperature-dependent magnetic properties in anti-ferromagnet (AFM) and ferromagnet (FM) structure were investigated with the aid of a physical property measurement system (PPMS). It was observed that magnetic interactions between the AFM (Mn) and FM (CoFe2O4) material arise below the Neel temperature of the dopant. Furthermore, hysteresis response was clearly pronounced for the enhancement in magnetic parameters by varying temperature towards absolute zero. It is shown that magnetic properties have been tuned as a function of temperature and an externally-applied field.
A comprehensive study on thermal stability and magnetic properties of MnZn-ferrite nanoparticles
Abstract Nanoparticles of MnxZn1-xFe2O4 (0 ≤ x ≤ 1.0) compositions were synthesized via sol-gel process. The structure, thermal stability and magnetic properties of as-prepared and annealed samples have been investigated. Although, as-prepared and 1200 °C air annealed samples exhibit cubic spinel ferrite phase, they decompose into α-Fe2O3, or/and α-Mn2O3 phases along with the poor quality of ferrite phase on annealing at 600 °C in air. Present investigations show that the stability of spinel ferrite phase is sensitive to (i) Mn concentration (ii) the annealing temperature and (iii) environments (air, Oxygen and Argon atmosphere) in which annealing experiments were carried out. A comparative study of structural and magnetic properties of Argon and air annealed samples suggest that differential oxygen partial pressure plays a significant role in stability as well as magnetic properties. Therefore, we suggest the deterioration of magnetic properties in Mn-Zn ferrite nanoparticles is due to depletion of Fe3+ ions from spinel structure that affects the cation distribution. It is also shown that magnetic properties can be tuned by controlling the process conditions. From these studies we propose a phenomenological model which explains the observation of present study.
Synthesis and characterization of highly ordered BiFeO3 multiferroic nanowire arrays
Abstract We report the synthesis and characterization of multiferroic BiFeO 3 (BFO) nanowires. The perovskite BFO nanowires with diameters about 60 nm and lengths about 10 μm were fabricated by means of the sol-gel method utilizing nanochannel alumina templates with post annealing at 700 °C. The microstructure of the BFO nanowires was investigated by means of x-ray diffraction and transmission electron microscopy, and the ferroelectric characteristic of BFO nanowires were demonstrated.