MSResearch Areas
My research group has numerous ongoing research activities on the physics and applications of 'Nanostructured thins film and nanomaterials' and 'Advance materials'. Our research areas include, growth of ZnO nanostructures and doped ZnO for white light emission and UV detection; Magnetic nanoparticles (MNPs)-understanding the physics of small magnetic particles and applications of MNPs in magnetic hypothermia and water purification; Fabrications of magnetic tunnel junctions; magnetoelectric coupling studies in multiferroics;Nanocrystalline diamond (NCD) wear resistant coatings on WC dies, end mills etc. for industrial applications; Nanosystems (nanotitania and CIS) for alternative photovoltaic applications.
Magnetism
Spin transport in Oxide heterostructures
Spintronics is an emerging technology, which has been extensively investigated in the recent past. Generation, transportation and detection of spin in a controlled manner are very important in spintronic devices. There are several ways one can generate spin current for example from spin Seebeck effect and spin pumping effect. The conversion of charge current to spin current is known as Spin Hall Effect (SHE) and the inverse phenomenon is Inverse SHE (ISHE). The detection of spin is usually realized by the ISHE. The paramagnetic metals such as Pt, W and Ta are widely used for ISHE. Recently, Spin Hall magnetoresistance (SMR) has been studied as an important tool to investigate the conversion of charge to spin and vice-versa. SMR arises due to the simultaneous effect of SHE and ISHE in a bilayer heterostructures consisting of ferromagnetic (or ferrimagnetic) insulator and a normal metal (NM).
ADMR data of a Bi:YIG(54)/Pt(4) bilayer (panels (a), (c), and (e)) and a Bi:YIG(54)/Ga:ZnO(8)/Pt(4) trilayer (panels (b), (d), and (f)) sample grown on YAG (111) substrates.
Magnetic Proximity Effect (MPE) observed in YIG/Pt complicates the spin transport scenario with additional effects such as Anomalous hall effect (AHE) which attenuate SMR signal.7. Our group has successfully studied Ga: ZnO insertion on Bi: YIG/Pt and observed SMR signals, but the increase in spurious paramagnetic signal hampered the SMR signals with increasing Ga: ZnO thickness6. A solution for this is to employ antiferromagnetic moments, which are quite stable to stray fields and MPE. Recent studies in this direction has proved successful in generating spin current using antiferromagnetsNiO/Pt, Cr2O3/W, CuIr and SrMnO3/Pt layers8,9,10. Recent theories and experiments carried out by various groups to use spin current as a detection method to probe interface magnetism in heterostructures. Currently we are working on this direction with our German Collaborators (Prof. Rudolf Gross, WMI Garching, Germany)
Magnetic Nanoparticles Synthesis, physics and applications
Synthesis and assembly of magnetic nanoparticles have attracted great attention because of their potential application in ultrahigh-density magnetic recording, ferrofluids, magnetic resonance imaging (MRI), cell and DNA separation, magnetically guided drug delivery, magnetic fluid hyperthermia (MFH), etc. The size distribution of the nanoparticles is one of the key parameters that determine the physical and chemical properties of the nanocomposite. Magnetic hyperthermia is a type of cancer treatment proposed to increase the temperature of the body tissue to about 42oC using the heat generated from magnetic nanoparticles. Conventional cancer treatment methods such as surgery, chemotherapy and radiotherapy have side effects associated with them and hence MFH is considered as an alternative in cancer therapy. The MFH is claimed to destroy cancer cells selectively, when the nanoparticles are surface modified for their selective absorption on cancer cells.
Fig: FESEM image of magnetite nanoparticles with an average particle size 6 ± 2 nm and a.c. susceptibility measurements showing the variation in the peak maximum temperature with variation in applied frequency.
