Synthesis and physicochemical properties of doped nano oxides-dilute magnetic semiconductors

Doped nano oxides based dilute magnetic semiconductors such as Zn_0.97Fe_0.03O, Ce_0.8Nd_0.2O₂, Sn_0.99Mn_0.01O₂, Ni_0.99Fe_0.01O, and γ-Fe₂O₃ have synthesized by the chemical coprecipitation method. These powders have been characterized with respect to compositional analysis (ICPES and EDAX), structural analysis (XRD), morphology (TEM), semiconducting properties (d.c. electrical conductivity, thermoelectric powder, and Hall effect measurements), dielectric properties and magnetization measurements (VSM and SQUID magnetometer). A slight decrease in the lattice parameter has observed for all compounds. The SAED pattern exhibited the lattice planes which indicate that the particle is crystalline with no defect. The infrared spectra of these compounds reveal two absorption bands associated with the stretching and bending vibrations. From TEM images, the average particle size of these oxides has found between 10 to 81 nm, which confirmed the nano-sized oxides have formed. The temperature of conductivity for all doped nano oxides showed a definite break which corresponding to extrinsic to intrinsic semiconducting properties. Thermoelectric power (TEP) and Hall effect measurements for all compounds are found to be n-type semiconductors. Magnetization measurement at room temperature gave a typical hysteresis loop for all compounds except Sn_0.99Mn_0.01O₂, indicating room temperature ferromagnetism. The observed magnetism is due to the exchange interaction between the defect and magnetic dopant ions. The Sn_0.99Mn_0.01O₂ sample showed to be antiferromagnetism. The zero-field cooled and field-cooled magnetization measurement in temperature range 5–325 K at 100 Oe confirmed the coexistence of magnetic coupling in the sample.