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Title: Search for ferromagnetism in undoped and cobalt-doped HfO{sub 2-{delta}}

Abstract

We report on the search for ferromagnetism in undoped and cobalt-doped high-k dielectric HfO{sub 2} films. Over a broad range of growth conditions, we do not observe ferromagnetism in undoped HfO{sub 2} films. On the other hand, we do observe room temperature ferromagnetism in dilutely Co-doped HfO{sub 2} films, but the origin of the same appears extrinsic (a Co rich surface layer) at least for the regime of growth conditions explored.

Authors:
; ; ; ; ; ; ; ; ; ; ; ; ; ;  [1];  [2];  [2];  [2];  [2];  [2] more »;  [2] « less
  1. Center for Superconductivity Research, Department of Physics, University of Maryland, College Park, Maryland 20742-4111 (United States)
  2. (United States)
Publication Date:
OSTI Identifier:
20779164
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Physics Letters; Journal Volume: 88; Journal Issue: 14; Other Information: DOI: 10.1063/1.2190909; (c) 2006 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; COBALT; DIELECTRIC MATERIALS; DOPED MATERIALS; ENERGY LOSSES; FERROMAGNETIC MATERIALS; FERROMAGNETISM; HAFNIUM OXIDES; ION MICROPROBE ANALYSIS; MASS SPECTRA; MASS SPECTROSCOPY; SCANNING ELECTRON MICROSCOPY; TEMPERATURE RANGE 0273-0400 K; THIN FILMS; TRANSMISSION ELECTRON MICROSCOPY; X-RAY PHOTOELECTRON SPECTROSCOPY

Citation Formats

Ramachandra Rao, M.S., Kundaliya, Darshan C., Ogale, S.B., Fu, L.F., Welz, S.J., Browning, N.D., Zaitsev, V., Varughese, B., Cardoso, C.A., Curtin, A., Dhar, S., Shinde, S.R., Venkatesan, T., Lofland, S.E., Schwarz, S.A., Department of Chemical Engineering and Materials Science, University of California at Davis, California 95616 and Lawrence Berkeley National Laboratory, NCEM, One Cyclotron Road, Berkeley, California 94720, Department of Material Science and Engineering, Stony Brook University, Stony Brook, New York 11790, Department of Chemistry, University of Maryland, College Park, Maryland 20742, Center for Superconductivity Research, Department of Physics, University of Maryland, College Park, Maryland 20742-4111, Department of Physics, Rowan University, 201 Mullica Hill Road, New Jersey 08028-1701, and Department of Physics, Queens College of CUNY, Flushing, New York 11367. Search for ferromagnetism in undoped and cobalt-doped HfO{sub 2-{delta}}. United States: N. p., 2006. Web. doi:10.1063/1.2190909.
Ramachandra Rao, M.S., Kundaliya, Darshan C., Ogale, S.B., Fu, L.F., Welz, S.J., Browning, N.D., Zaitsev, V., Varughese, B., Cardoso, C.A., Curtin, A., Dhar, S., Shinde, S.R., Venkatesan, T., Lofland, S.E., Schwarz, S.A., Department of Chemical Engineering and Materials Science, University of California at Davis, California 95616 and Lawrence Berkeley National Laboratory, NCEM, One Cyclotron Road, Berkeley, California 94720, Department of Material Science and Engineering, Stony Brook University, Stony Brook, New York 11790, Department of Chemistry, University of Maryland, College Park, Maryland 20742, Center for Superconductivity Research, Department of Physics, University of Maryland, College Park, Maryland 20742-4111, Department of Physics, Rowan University, 201 Mullica Hill Road, New Jersey 08028-1701, & Department of Physics, Queens College of CUNY, Flushing, New York 11367. Search for ferromagnetism in undoped and cobalt-doped HfO{sub 2-{delta}}. United States. doi:10.1063/1.2190909.
Ramachandra Rao, M.S., Kundaliya, Darshan C., Ogale, S.B., Fu, L.F., Welz, S.J., Browning, N.D., Zaitsev, V., Varughese, B., Cardoso, C.A., Curtin, A., Dhar, S., Shinde, S.R., Venkatesan, T., Lofland, S.E., Schwarz, S.A., Department of Chemical Engineering and Materials Science, University of California at Davis, California 95616 and Lawrence Berkeley National Laboratory, NCEM, One Cyclotron Road, Berkeley, California 94720, Department of Material Science and Engineering, Stony Brook University, Stony Brook, New York 11790, Department of Chemistry, University of Maryland, College Park, Maryland 20742, Center for Superconductivity Research, Department of Physics, University of Maryland, College Park, Maryland 20742-4111, Department of Physics, Rowan University, 201 Mullica Hill Road, New Jersey 08028-1701, and Department of Physics, Queens College of CUNY, Flushing, New York 11367. Mon . "Search for ferromagnetism in undoped and cobalt-doped HfO{sub 2-{delta}}". United States. doi:10.1063/1.2190909.
@article{osti_20779164,
title = {Search for ferromagnetism in undoped and cobalt-doped HfO{sub 2-{delta}}},
author = {Ramachandra Rao, M.S. and Kundaliya, Darshan C. and Ogale, S.B. and Fu, L.F. and Welz, S.J. and Browning, N.D. and Zaitsev, V. and Varughese, B. and Cardoso, C.A. and Curtin, A. and Dhar, S. and Shinde, S.R. and Venkatesan, T. and Lofland, S.E. and Schwarz, S.A. and Department of Chemical Engineering and Materials Science, University of California at Davis, California 95616 and Lawrence Berkeley National Laboratory, NCEM, One Cyclotron Road, Berkeley, California 94720 and Department of Material Science and Engineering, Stony Brook University, Stony Brook, New York 11790 and Department of Chemistry, University of Maryland, College Park, Maryland 20742 and Center for Superconductivity Research, Department of Physics, University of Maryland, College Park, Maryland 20742-4111 and Department of Physics, Rowan University, 201 Mullica Hill Road, New Jersey 08028-1701 and Department of Physics, Queens College of CUNY, Flushing, New York 11367},
abstractNote = {We report on the search for ferromagnetism in undoped and cobalt-doped high-k dielectric HfO{sub 2} films. Over a broad range of growth conditions, we do not observe ferromagnetism in undoped HfO{sub 2} films. On the other hand, we do observe room temperature ferromagnetism in dilutely Co-doped HfO{sub 2} films, but the origin of the same appears extrinsic (a Co rich surface layer) at least for the regime of growth conditions explored.},
doi = {10.1063/1.2190909},
journal = {Applied Physics Letters},
number = 14,
volume = 88,
place = {United States},
year = {Mon Apr 03 00:00:00 EDT 2006},
month = {Mon Apr 03 00:00:00 EDT 2006}
}
  • Undoped and Ni (5 at.%) doped In{sub 2}O{sub 3} thin films were deposited on glass substrate using electron beam evaporation technique and Ni doped In{sub 2}O{sub 3} thin films were annealed at 450 oC. A systematic study was carried out on the structural, chemical and magnetic properties of the as deposited and annealed thin films. X-ray diffraction analysis revealed that all the films were cubic in structure and exhibied ferromagnetism at room temperature. The undoped In{sub 2}O{sub 3} thin films exhibited a saturation magnetization of 24.01 emu/cm3. Ni doped In{sub 2}O{sub 3} thin films annealed at 450 oC showed amore » saturation magnetization of 53.81 emu/cm3.« less
  • Undoped indium oxide films with room temperature d{sup 0} ferromagnetism were prepared by radiofrequency magnetron sputtering with different O{sub 2}/Ar flux ratio. The optical and magnetic properties changed non-monotonously as the oxygen flux increases. A conversion of conductivity from n-type to p-type was observed as the flux ratio reached 15:15. The concordant results in structural, electrical, optical, and magnetic properties suggest that single ionized oxygen and indium vacancies play crucial roles in mediating the ferromagnetism in n and p-type In{sub 2}O{sub 3} films, respectively.
  • Highlights: • Undoped In{sub 2}O{sub 3} nanowires were synthesized by a thermal evaporation method. • In{sub 2}O{sub 3} nanowires show d{sup 0} ferromagnetism at room temperature. • Large amount of defects were confirmed by PL, UV/vis, and XPS. • Oxygen deficient surfaces and size effect mediating ferromagnetic ordering. - Abstract: We report the observation of intrinsic room-temperature ferromagnetism in undoped In{sub 2}O{sub 3} nanowires synthesized by a thermal evaporation method. The as-grown sample was characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), temperature-dependent photoluminescence (PL), Ultraviolet–visible spectroscopy (UV/vis), X-ray photoelectron spectroscopy (XPS), andmore » superconducting quantum interference device (SQUID). Structural characterizations show that the as-grown sample is single crystal cubic bixbyite structure with 80–100 nm in diameter and 2–4 μm long. Both PL and UV/vis results reveal that the sample exhibits large amount of oxygen vacancies and indium vacancies (V{sub O} and V{sub In}). XPS results indicate that the In{sub 2}O{sub 3} nanowires are significantly oxygen deficient and non-stoichiometric at surface. Experimentally measured magnetic hysteresis curves for undoped In{sub 2}O{sub 3} nanowires clearly display ferromagnetic behavior at room temperature. We believe the ferromagnetism of undoped In{sub 2}O{sub 3} nanowires is ascribed to the large surface area and intrinsic defects mediating the ferromagnetic ordering.« less
  • Based on first-principles calculations, the coexistence of Ti vacancies (V{sub Ti}) and O vacancies (V{sub O}) is first considered to study the origin of the ferromagnetic ordering in undoped rutile TiO{sub 2}. The calculations show that V{sub O} can induce local magnetic moments in TiO{sub 2}, however, the ferromagnetic (FM) exchange interaction of two V{sub O} is not strong enough to induce room-temperature (RT) ferromagnetism on their own in undoped TiO{sub 2}. The FM coupling between two V{sub Ti} is about four times stronger than that between two V{sub O}. More importantly, the FM coupling between two V{sub Ti} ismore » further enhanced after V{sub O} is introduced. Our results indicate that the electrons induced by V{sub O} mediate the long-range FM exchange interaction between two distant V{sub Ti}. This maybe the ferromagnetism mechanism in undoped TiO{sub 2}: V{sub Ti} produce local moments while the electrons induced by V{sub O} mediated the long-range FM exchange interaction. The results are in excellent agreement with the experimental evidences that V{sub O} alone cannot induce RT ferromagnetism while V{sub O} can promote the ferromagnetic ordering in undoped TiO{sub 2}.« less
  • Resistivity and DC magnetization measurements were performed for the polycrystalline Pr{sub 0.5}Ca{sub 0.5}Co{sub 1-x}Fe{sub x}O{sub 3-{delta}} (x=0,0.05,0.10 and 0.15) samples. The as-fabricated samples exhibit ferromagnetic (FM) transition and the transition temperature increases with increasing the Fe doping level. Annealing under the high oxygen pressure induces a spin-state transition of Co ions in the iron-free sample and such transition is reinforced with increasing the annealing oxygen pressure, while the annealing under high oxygen pressure suppresses the ferromagnetic ordering. Contrary to the case of the iron-free sample, no spin-state transition is induced by the annealing under high oxygen pressure for the Fe-dopedmore » samples, and the ferromagnetic transition temperature is nearly independent of the annealing procedures. The enhancement of the spin-state transition in the iron-free sample after annealing under high oxygen pressure should be attributed to the oxygen vacancies and the reduction of the cell volume. The suppression of the spin-state transition by the Fe doping is related to the enlargement of the cell volume. The enhancement of the ferromagnetism by the Fe-doping might arise from the ferromagnetic exchange interaction between Fe{sup 3+} and LS Co{sup 4+} through oxygen atom (Fe{sup 3+}-O-Co{sup 4+})« less