Sujeet Chaudhary

SPIN-POLARIZED TUNNELING IN THE HALF-METALLIC FERROMAGNETS LA0.7-XHOXSR0.3MNO3 (X=0 AND 0.15) : EXPERIMENT AND THEORY

The magnetoresistance (MR) in polycrystalline colossal magnetoresistive compounds follows a behavior different from single crystals below the ferromagnetic transition temperature. This difference is usually attributed to spin polarized tunneling at the grain boundaries of the polycrystalline sample. Here we derive a theoretical expression for the contribution of spin polarized tunneling to the magnetoresistance in granular ferromagnetic systems under the mean field approximation. We apply this model to our experimental data on the half metallic ferromagnet La0.7Sr0.3MnO3, and find that the theoretical predictions agree quite well with the observed dependence of the spin polarized MR on the spontaneous magnetization.

Room temperature ferromagnetism in Mn doped TiO2 thin films: Electronic structure and Raman investigations

In this work dc-magnetization, electronic structural, and Raman investigations of Ti1−xMnxO2 (x = 0.00, 0.05, 0.10, and 0.15) thin films deposited on fused-quartz substrate by a simple and cost effective spray pyrolysis technique have been reported. X-ray diffraction revealed the formation of pure anatase TiO2 phase devoid of elemental Mn clusters in all the Mn incorporated TiO2 films. It is established by x-ray photoelectron spectroscopic (XPS) measurements that Ti ions substituted by Mn ions in both divalent and trivalent states in the TiO2 matrix. No peak corresponding to Mn+4 could be evidenced by XPS. The Raman study has further established the formation of TiO2 in anatase structure in both pure TiO2 and Mn-doped TiO2 films. The Ti1−xMnxO2 films with x ≥ 0.05 exhibit ferromagnetic ordering at room temperature which arises most likely due to formation of bound magnetic polarons.

High temperature ferromagnetism in Mn-doped SnO2 nanocrystalline thin films

It has been possible to induce room temperature ferromagnetism, exhibiting high transition temperature, in tin oxide thin films by introducing manganese in a SnO2 lattice. The observed temperature dependence of the magnetization predicts a Curie temperature exceeding 550 K. A maximum saturation magnetic moment of 0.18±0.04 μB per Mn ion has been estimated for spray pyrolized Sn1−xMnxO2−δ thin films, with x=0.10. For Mn concentration (x) higher than 0.10, the films show linear behavior. The magnetization-versus-field studies indicate that the origin of ferromagnetism lies neither in ferromagnetic metal clusters nor in the presence of metastable phases. The structure factor calculations reveal that Mn has been incorporated in the SnO2 lattice. Also, the electron transport investigation indicates that there is a change of Mn occupancy from substitutional to interstitial sites of the SnO2 lattice when the Mn concentration exceeds 7.5 at. %. These films do not exhibit anomalous Hall effects at room temperature...

First-order transition from antiferromagnetism to ferromagnetism inCe(Fe0.96Al0.04)2

Results of dc magnetization study are presented showing interesting thermomagnetic history effects across the antiferromagnetic to ferromagnetic transition in Ce(Fe

Growth and characterization of TiAlN∕CrAlN superlattices prepared by reactive direct current magnetron sputtering

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Cobalt-substituted SnO2 thin films: A transparent ferromagnetic semiconductor

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Intrinsic and extrinsic origin of room temperature ferromagnetism in ZnO:Co (5at.%)

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Observation of room temperature ferromagnetism in nanocrystalline ZnO?:?Co system

. Specifically, we observe (i)ZFC/FC irreversibility rising with increasing field; (ii) virgin curve lying outside the envelope M-H curve. We argue that these effects are quite different from the characteristics seen in spin-glasses or in hard ferromagnets; they can be understood as metastabilities associated with a first order magnetic phase transition.

Magnetocaloric effect in La1−xSrxCoO3 (0.05⩽x⩽0.40)

TiAlN and CrAlN coatings were prepared using a reactive direct current magnetron sputtering system from TiAl and CrAl targets. Structural characterization of the coatings using x-ray diffraction (XRD) revealed the B1 NaCl structure of TiAlN and CrAlN coatings with a prominent reflection along the (111) plane. The XPS data confirmed the bonding structures of TiAlN and CrAlN single layer coatings. Subsequently, nanolayered multilayer coatings of TiAlN∕CrAlN were deposited on silicon and mild steel (MS) substrates at different modulation wavelengths (Λ) with a total thickness of approximately 1.0μm. The modulation wavelengths were calculated from the x-ray reflectivity data using modified Bragg’s law. TiAlN∕CrAlN multilayer coatings were textured along (111) for Λ<200A and the XRD patterns showed the formation of superlattice structure for coatings deposited at Λ=102A. The x-ray reflectivity data showed reflections of fifth and seventh orders for multilayer coatings deposited at Λ=102 and 138A, respectively,...

Interfacial Charge Induced Magnetoelectric Coupling at BiFeO3/BaTiO3 Bilayer Interface

A maximum room temperature ferromagnetic moment of 0.47μB∕Co ion has been observed in Sn0.9Co0.1O2−δ films grown by spray pyrolysis. The films have high conductivity (∼150Ω−1cm−1) and ∼70% transmittance in the visible region. A systematic variation of saturation magnetization, carrier concentration, electrical conductivity, and optical transmission edge in Sn1−xCoxO2−δ(0.05⩽x⩽0.15) films is correlated with the change in Co concentration, and a carrier mediated Ruderman-Kittel-Kasuya-Yoshida interaction has been proposed as the most probable mechanism for the ferromagnetic ordering. The maximum blueshift in the transmission edge by ∼215meV (at x=0.10) is attributed to the extra carriers generated by Co substitution.