Magnetic & Spintronics Material

Nanomagnetism: Nano FerritesLithium ferrite, Bismuthferrite,Barium ferrite etc have been designed & developed for microwave applications. Fe-doped PbTiO3 nanoparticles have been synthesized by chemical route using polyvinyl alcohol as a surfactant. The role of surfactant & nanosize has been analyzed to explain enhancement of magnetization value of Fe doped nanoparticles of lead titnate to 41.6 x 10-3 emu/g.

Ferrite Materials for Microwave application: Ferrites are basically ferromagnetic oxide materials possess high resistivity and permeability. He has been working on ferrite since 1991. He started synthesizing hard ferrite thin films for magneto-optical properties. His experience in ferrite covers from hard ferrite BaFe12O19 to almost all soft ferrites e.g. Li0.5Fe2.5O4, Mn1-xZnxFe2O4, NiFe2O4, MgFe2O4. An increase in magnetization 79.39 emu/g had been obtained by doping nano SiO2 due to the dilution of magnetization of the A-sublattice by non magnetic Si4+ ions in spinel type LiCd ferrite. Soft ferrites composites with conducting polymers have been explored for microwave absorbing materials. 

Nanotechnology for EMI Shielding: For the first time improved electromagnetic interference shielding response was established in Poly(aniline)-coated fabrics by substituting dielectric and magnetic Nanoparticles of BaTiO3 (15 nm) or Fe3O4 (40 nm) within coated poly (aniline)(PANI) matrix. The high value of absorption-dominated SET (97 % attenuation) and specific shielding effectiveness value of 18 dB cm3/g demonstrated.

Multiferroic Materials: He applied his rich knowledge and experience in ferrite for the emerging multiferroic and spintronic field. In multiferroic, ferromagnetism was induced in nonmagnetic chromium doped ferroelectric barium titanate. Induced electric polarization is obtained on applying external magnetic field due to local interaction of d electron spins with disordered electric dipoles via oxygen vacancies created by Cr doping in BaTiO3. Structural phase transformation from tetragonal to distorted cubic phase was achieved due to doping. In order to observe enhanced magnetoelectric coupling, bilayer and trilayer thin films of BiFeO3/BaTiO3 has been grown by RF sputtering techniques. On multiferroics-Office of Naval Research (ONR), Washington, USA had entrusted work on multiferroics for development of electromagnetic sensor with Italy group and awarded 0.105 million $ US as a contract project in 2010.

The ME coupling coefficient of 1.5Cr:BTO at room temperature maximum value of ‘α’ obtained 13 mV cm-1Oe-1 for 2800 Oe.( J. Mater. Chem. A , 2013, 1, 8601-8608).

Multiferroic BiFeO3/BaTiO3 bilayer, Appl. Mater. Interfaces 7, 8472, 2015.

Spin Hall Effect (Spintronic) Materials: Colossal magnetoresistive materials like Sr2FeMoO6, La1-xPbxMnO6 have been explored for spintronic application. Sr2FeMoO6 (SFMO) is a 100% spin polarized half-metallic SFMO exhibits a high Curie temperature (>400 K) and excellent magnetoresistance properties at low field, making it very promising candidate for Magnetic Tunnel Junction (MTJs). Tri-layer of SFMO/SrTiO3/SFMO structure on STO buffered Si (100) substrate has been fabricated by Pulsed laser deposition technique for MTJ. The TMR value ~7% at room temperature is attributed to spin dependent tunneling across a uniform ultrathin STO tunnel barrier sandwiched between two identical SFMO electrodes.

Room Temperature Metal-Insulator Transition has been observed in Pb substituted Lanthanum Manganite.

Magnetic Tunnel Junction-SFMO/STO/SFMO Journal of Physics D: Applied Physics 47 (6), 065006.

Diluted Magnetic Semiconductor: In major breakthrough room temperature ferromagnetism in ZnO doped by Lithium as diluted magnetic semiconductor had been acheived. A comprehensive theory had been given based on correlated model for oxygen orbital with random potentials introduced by Li atoms which ultimately inducing local magnetic moments on oxygen atoms. Physical Rev. B, 79, 2009.

Microwave Induced Spin-Hall Effect (SHE): SHE to be used for spintronic devices, magnetic memory, spin logic gates, microwave signal generator of Nano size and single electron transistor applications. Influence on Ferromagnetic Resonance Signal of Perpendicular Magnetic Anisotropic Co/Pt Bilayer due to weak spin pumping had been investigated first time in India. Bilayer paramagnetic and ferromagnetic thin film Pt/FeSi3% has been fabricated for microwave nano oscillator device applications.

Schematic of microwave induced SHE in Co/Pt (microwave nano oscillator)

Humidity Sensor: A highly humidity sensitive oxygen deficient porous magnesium ferrite has been developed and its conduction mechanism by physisorbed water layers has been established experimentally & theoretically through isosteric heat of adsorption, binding energy of water molecules. Further oxygen deficient porous magnesium ferrite thin films by Pulse Laser Deposition, PLD, have been developed showing Colossal Humido-Resistance (CHR) change with humidity which can be very well exploited for device application.