Dilute Magnetic Semiconductor
Dilute Magnetic Semi-conductors (DMS’s) have attracted considerable attention in recent years because of their potential for novel applications in the rapidly evolving area of spintronics (where the spin and charge degrees of freedom are utilized simultaneously). While most of the DMS’s have low Curie temperature (Tc), CoxTi(1-x)O2 anatase and rutile has been observed to have high Tc (~400K). Furthermore, CoxTi(1-x)O2 is transparent in the visible and near infrared regions with a sizable band gap and appreciable conductivity. Therefore, it is believed to be very useful candidate in the fabrication of magnetic semiconductor devices in general. However, these accomplishments depend on the progress in understanding, predicting and controlling the physical properties of such a material. For example, due to the intrinsic complexities, the underlying microscopic mechanism of long range magnetic ordering and even the way of Co distribution is in CoxTi(1-x)O2 are still unclear. Also the dependence of structural transformation on the synthesis conditions (e.g. O2 partial pressure, temperature etc.) which culminate in the considerable change of magnetic and transport properties accordingly needs to be explored in detail. Moreover, by controlling certain parameters during synthesis, one can tune different properties of these materials e.g. tuning of magnetic and/or transport properties with oxygen vacancies or some defect sites. In order to study the aforementioned problems in depth, we synthesize CoxTi(1-x)O2 via chemical routs (e,g sol-gel), sputtering techniques and laser ablated deposition. Apart from the synthesis, we characterize the materials for various characterizations using X-ray diffraction (XRD), scanning electron microscopy (SEM), tunneling electron microscopy (TEM), atomic force microscopy (AFM) etc. X-ray Photoelectron Spectroscopy (XPS), UV Visible spectrophotometry, etc., are used to study the electronic behavior (e.g. band gap information etc). We use the standard four probe technique to study the electrical transport properties. Physical properties measurements system (PPMS) and SQUID are used to study the magnetic properties.