@article{mal_nori_narayan_prater_avasthi_2013, title={Ion-irradiation-induced ferromagnetism in undoped ZnO thin films}, volume={61}, ISSN={["1359-6454"]}, DOI={10.1016/j.actamat.2012.09.071}, abstractNote={We have introduced defects in ZnO epitaxial thin films by swift heavy 107Ag9+ ion irradiation and investigated systematically their magnetic, electrical and optical properties. Oxygen annealed ZnO films are epitaxial single crystals that exhibit no long-range magnetic order. However, in this paper it is shown that room-temperature ferromagnetism (RTFM) can be introduced in a controlled manner in these films using ion irradiation and that the magnetization increases with ion dose. This qualitatively agrees with earlier studies which showed that RTFM could be induced in ZnO films through either vacuum thermal annealing or pulsed laser annealing below energy densities that lead to melting. Raman studies of the ion irradiated samples revealed dramatic changes in the vibration modes that correlated with increases in the carrier concentration, indicative of lattice disorder and defect creation. We compare these results with those observed in laser irradiated and vacuum annealed samples, and then discuss these findings in the context of defects and defect complexes created during the high-energy heavy ion irradiation process. We propose a unified mechanism to explain RTFM and n-type conductivity enhancements during irradiation, and laser and vacuum annealing.}, number={8}, journal={ACTA MATERIALIA}, author={Mal, Siddhartha and Nori, Sudhakar and Narayan, J. and Prater, J. T. and Avasthi, D. K.}, year={2013}, month={May}, pages={2763–2768} }
 @article{gupta_dutta_mal_narayan_2012, title={Controlled p-type to n-type conductivity transformation in NiO thin films by ultraviolet-laser irradiation}, volume={111}, number={1}, journal={Journal of Applied Physics}, author={Gupta, P. and Dutta, T. and Mal, S. and Narayan, J.}, year={2012} }
 @article{mal_nori_mula_narayan_prater_2012, title={Defect mediated reversible ferromagnetism in Co and Mn doped zinc oxide epitaxial films}, volume={112}, number={11}, journal={Journal of Applied Physics}, author={Mal, S. and Nori, S. and Mula, S. and Narayan, J. and Prater, J. T.}, year={2012} }
 @article{yang_nori_mal_narayan_2011, title={Control of room-temperature defect-mediated ferromagnetism in VO2 films}, volume={59}, ISSN={["1359-6454"]}, DOI={10.1016/j.actamat.2011.06.047}, abstractNote={We report interesting ferromagnetic properties and their control in a vanadium-based oxide system driven by stoichiometric defects. Vanadium oxide (VO2) thin films were grown on c-plane sapphire substrates by a pulsed laser deposition technique under different ambient conditions. The ferromagnetism of the epitaxial VO2 films can be switched on and off by altering the cooling ambient parameters. In addition, the saturated magnetic moments and coercivity of the VO2 films were found to be a function of the oxygen partial pressure during the growth process. The room-temperature ferromagnetic properties of VO2 films were correlated with the nature of the microstructure and the growth parameters. The origin of the induced magnetic properties are qualitatively understood to stem from intrinsic structural and stoichiometric defects.}, number={16}, journal={ACTA MATERIALIA}, author={Yang, Tsung-Han and Nori, Sudhakar and Mal, Siddhartha and Narayan, Jagdish}, year={2011}, month={Sep}, pages={6362–6368} }
 @article{mal_nori_narayan_prater_2011, title={Defect-mediated ferromagnetism and controlled switching characteristics in ZnO}, volume={26}, ISSN={["2044-5326"]}, DOI={10.1557/jmr.2011.74}, abstractNote={Abstract}, number={10}, journal={JOURNAL OF MATERIALS RESEARCH}, author={Mal, Siddhartha and Nori, Sudhakar and Narayan, Jagdish and Prater, John T.}, year={2011}, month={May}, pages={1298–1308} }
 @article{mal_yang_gupta_prater_narayan_2011, title={Thin film epitaxy and magnetic properties of STO/TiN buffered ZnO on Si(001) substrates}, volume={59}, ISSN={["1873-2453"]}, DOI={10.1016/j.actamat.2010.12.058}, abstractNote={Abstract We report integration of epitaxial ZnO films with Si(0 0 1) substrates using STO/TiN buffer layers. It has been demonstrated that the preferential orientation of the a-plane ( 1 1 2 ¯ 0 ) and c-plane (0 0 0 2) of ZnO can be controlled via deposition temperature and oxygen partial pressure. At lower substrate temperatures ZnO grows solely in the (0 0 0 2) orientation, while the ( 1 1 2 ¯ 0 ) orientation was dominant at high substrate temperatures and low oxygen pressures. At higher pressures, the (0 0 0 2) orientation is preferred, while ( 1 1 2 ¯ 0 ) becomes weaker and a ( 1 0 1 ¯ 2 ) ZnO appears. Epitaxial relationships have been determined from X-ray diffraction φ-scans and it was found that both c- and a-ZnO had two types of orientations due to the cubic symmetry of the STO buffer layer. The orientation relationship of c-ZnO on STO(0 0 1) was ZnO(0 0 0 1) ∥ STO(1 0 0); ZnO[ 1 1 2 ¯ 0 ] ∥ STO[1 1 0] and ZnO[ 1 ¯ 2 1 ¯ 0 ] ∥ STO[ 1 ¯ 1 0 ], while that of a-ZnO on STO(0 0 1) was ZnO( 1 1 2 ¯ 0 ) ∥ STO(1 0 0); ZnO[ 1 1 2 ¯ 0 ] ∥ STO[1 1 0] and ZnO[0 0 0 2] ∥ STO[ 1 ¯ 1 0 ]. High-resolution transmission electron microscopy studies revealed atomically sharp interfaces with no reaction at the interface. Reversible d0 ferromagnetism was found to be present in both ZnO and STO layers. Our electron-energy-loss spectroscopy studies conclusively rule out the presence of any external ferromagnetic ions or impurities. Taken together, our data indicate that the ferromagnetic order in these undoped oxides might be defect mediated.}, number={6}, journal={ACTA MATERIALIA}, author={Mal, Siddhartha and Yang, Tsung-Han and Gupta, P. and Prater, J. T. and Narayan, J.}, year={2011}, month={Apr}, pages={2526–2534} }
 @article{mal_nori_jin_narayan_nellutla_smirnov_prater_2010, title={Reversible room temperature ferromagnetism in undoped zinc oxide: Correlation between defects and physical properties}, volume={108}, number={7}, journal={Journal of Applied Physics}, author={Mal, S. and Nori, S. and Jin, C. M. and Narayan, J. and Nellutla, S. and Smirnov, A. I. and Prater, J. T.}, year={2010} }