Ph.D, Indian Institute of Technology Bombay, India
My main work is Investigate the transport properties(Hall Effect, Resistivity etc.)in Heusler alloys
Currently spintronics and magnetocaloric effect are one of most emerging fields in condensed matter physics. The spintronic properties of the materials are not only due to the electron charge but it is combined effect of charge and spin of an electron and this offers opportunities for a new generation of devices. So the combination of conventional electronics with spin-dependent effects that arise from the interaction between spin and other properties of the materials are of typical use in spintronics . Spintronic is the manipulation and control of the spin of the electrons in solid state physics. There are many good materials theoretically and experimentally reported for spintronics devices application point of view, but to optimize the spintronic devices fully spin polarized materials are required. According to this requirement there are half metallic ferromagnetic (HMF) materials, which have 100% spin polarization in principle. HMF materials possess a conducting channel for one spin and a spin-semiconducting band gap . HMF materials are good for spin injection and spin polarization with high efficiency and thus maximizing the efficiency of spintronics devices. HMF behavior has been found in several types of materials such as magnetic oxides; dilute magnetic semiconductors, perovskites, double perovskites and Heusler alloys. Among these materials, Heusler alloys have a special place due to their higher Curie temperatures (TC) and tunable electronic structure. The magnetocaloric effect (MCE)is one of the hot area to do research, due to use these type materials as a cooling purpose. MCE is basically is a magneto-thermodynamic phenomenon in which a temperature change of a suitable material is caused by exposing the material to a external magnetic field. These type materials can be used as cooling purpose, because of their durability and environment friendly nature. Some Heusler compounds, oxides materials etc. have good MCE value. So Heusler alloys are also promising for cooling purpose.
Abstract: X-ray photoemission spectroscopy measurements were performed on thin-film samples of rutile Ti(1-x)Co(x)O(2-delta) to reveal the electronic structure. The Co 2p core-level spectra indicate that the Co ions take the high-spin Co2+ configuration, consistent with substitution on the Ti site. The high-spin state and the shift due to the exchange splitting of the conduction band suggest strong hybridization between carriers in the Ti 3d t(2g) band and the t(2g) states of the high-spin Co+2 . These observations support the argument that room temperature ferromagnetism in Ti(1-x)Co(x)O(2-delta) is intrinsic.
Pub.: 21 Feb '06, Pinned: 14 Sep '17
Abstract: Ferromagnetic semiconductors are believed to be suitable for future spintronics, because both charge and spin degrees of freedom can be manipulated by external stimuli. One of the most important characteristics of ferromagnetic semiconductors is the anomalous Hall effect. This is because the ferromagnetically spin-polarized carrier can be probed and controlled electrically, leading to direct application for electronics. Control of the Curie temperature and magnetization direction by electronic field, and photo-induced ferromagnetism have been performed successfully using the anomalous Hall effect for group III-V ferromagnetic semiconductors. In these cases, the operation temperature was much below room temperature because of the limited Curie temperature of less than 160 K (ref. 6). Here, we report on the anomalous Hall effect governed by electron doping in a room-temperature transparent ferromagnetic semiconductor, rutile Ti(1-x)Co(x)O(2-delta) (of oxygen deficiency delta). This result manifests the intrinsic nature of ferromagnetism in this compound, and represents the possible realization of transparent semiconductor spintronics devices operable at room temperature.
Pub.: 23 Mar '04, Pinned: 14 Sep '17
Abstract: Magnetic circular dichroism (MCD) of rutile Ti1-xCoxO2-d is systematically examined with various x and d to reveal a phase diagram for the appearance of ferromagnetism at higher carrier concentration and Co content. The phase diagram exactly matches with that determined from anomalous Hall effect (AHE). The magnetic field dependence of MCD also shows good coincidence with those of the magnetization and AHE. The coincidence of these independent measurements strongly suggests single and intrinsic ferromagnetic origin.
Pub.: 07 Apr '05, Pinned: 14 Sep '17
Abstract: Electric and magnetic properties of a high temperature ferromagnetic oxide semiconductor, cobalt-doped rutile TiO2, are summarized. The cobalt-doped rutile TiO2 epitaxial thin films with different electron densities and cobalt contents were grown on r-sapphire substrates with laser molecular beam epitaxy. Results of magnetization, magnetic circular dichroism, and anomalous Hall effect measurements were examined for samples with systematically varied electron densities and cobalt contents. The samples with high electron densities and cobalt contents show the high temperature ferromagnetism, suggesting that charge carriers induce the ferromagnetism.
Pub.: 24 May '08, Pinned: 14 Sep '17