Microwave processing of ZnO based dilute magnetic semiconductors

In the present work, polycrystalline ferromagnetic Zn_0.95Co_0.05O samples have been synthesized in a TM₀₁₁ single mode cylindrical microwave resonant cavity operating at 2.45 GHz. The synthesized specimen is analyzed for its crystallographic and electronic structure along with magnetic and electron transport properties. The X-ray diffractogram and photoelectron spectroscopy of Zn_0.95Co_0.05O establish the incorporation of cobalt atoms into ZnO lattice. The room temperature magnetization study confirms the ferromagnetic ordering in the microwave processed highly resistive samples; which can be attributed to bound magnetic polarons model.

I. Introduction

The microwave processing of materials in a multimode and/or single mode resonator cavity is emerging as an attractive new technology having unique advantages compared to conventional processing techniques. In conventional heating methods, thermal energy is transferred through the surface of the sample; as the penetration depth of the infrared radiation is very small , the heat transfer (from outer to interior of the sample) involving thermal conductivity mechanism is a time consuming phenomenon. Whereas, in microwave (MW) processing the MW energy is absorbed by the material and is then converted into thermal energy resulting in to volumetric heating, and very fast ramp up rate [1]–[3]. Also, it may even result in high reaction kinetics involving the individual constituents of the starting multiphase material.