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Enhanced Magnetization of Cobalt Defect Clusters Embedded in TiO2-δ Films

Journal Article · · ACS Applied Materials and Interfaces
 [1];  [2];  [2];  [3];  [4];  [4];  [5];  [6];  [7];  [8];  [6];  [6];  [6];  [6];  [9]
  1. Australian National Univ., Canberra, ACT (Australia); Univ. of Wollongong, NSW (Australia); Australian Nuclear Science and Technology Organisation (ANSTO), Lucas Heights, NSW (Australia)
  2. Max Planck Inst. fur Festkorperforschung, Stuttgart (Germany); Max Planck Society, Garching (Germany). Outstation at the MLZ
  3. Brookhaven National Lab. (BNL), Upton, NY (United States); Australian National Univ., Canberra, ACT (Australia)
  4. Australian National Univ., Canberra, ACT (Australia)
  5. Univ. of Wollongong, NSW (Australia)
  6. Australian Nuclear Science and Technology Organisation (ANSTO), Lucas Heights, NSW (Australia)
  7. Australian Nuclear Science and Technology Organisation (ANSTO), Lucas Heights, NSW (Australia); Univ. of New South Wales, Sydney, NSW (Australia)
  8. Australian Nuclear Science and Technology Organisation (ANSTO), Lucas Heights, NSW (Australia); Univ. of New South Wales, Sydney, NSW (Australia); California State Univ. (CalState), San Bernardino, CA (United States)
  9. Australian Nuclear Science and Technology Organisation (ANSTO), Lucas Heights, NSW (Australia); City Univ. of Hong Kong (China)
+ Show Author Affiliations
High magnetizations are desirable for spintronic devices that operate by manipulating electronic states using built-in magnetic fields. However, the magnetic moment in promising dilute magnetic oxide nanocomposites is very low, typically corresponding to only fractions of a Bohr magneton for each dopant atom. In this study, we report a large magnetization formed by ion implantation of Co into amorphous TiO2-δ films, producing an inhomogeneous magnetic moment, with certain regions producing over 2.5 μB per Co, depending on the local dopant concentration. Polarized neutron reflectometry was used to depth-profile the magnetization in the Co:TiO2-δ nanocomposites, thus confirming the pivotal role of the cobalt dopant profile inside the titania layer. X-ray photoemission spectra demonstrate the dominant electronic state of the implanted species is Co0, with a minor fraction of Co2+. The detected magnetizations have seldom been reported before and lie near the upper limit set by Hund’s rules for Co0, which is unusual because the transition metal’s magnetic moment is usually reduced in a symmetric 3D crystal-field environment. Low-energy positron annihilation lifetime spectroscopy indicates that defect structures within the titania layer are strongly modified by the implanted Co. We propose that a clustering motif is promoted by the affinity of the positively charged implanted species to occupy microvoids native to the amorphous host. This provides a seed for subsequent doping and nucleation of nanoclusters within an unusual local environment.
Research Organization:
Brookhaven National Laboratory (BNL), Upton, NY (United States)
Sponsoring Organization:
USDOE Office of Science (SC), Nuclear Physics (NP) (SC-26)
Grant/Contract Number:
SC0012704
OSTI ID:
1389242
Report Number(s):
BNL--114234-2017-JA
Journal Information:
ACS Applied Materials and Interfaces, Journal Name: ACS Applied Materials and Interfaces Journal Issue: 10 Vol. 9; ISSN 1944-8244
Publisher:
American Chemical Society (ACS)Copyright Statement
Country of Publication:
United States
Language:
English

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Cited By (3)

Two‐Dimensional Magnets: Forgotten History and Recent Progress towards Spintronic Applications journal May 2019
Clustering-induced high magnetization in Co-doped TiO2 journal September 2019
Structural and magnetic studies of TiO 2 rutile implanted with vanadium ions journal September 2019

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Related Subjects

73 NUCLEAR PHYSICS AND RADIATION PHYSICS
dilute magnetic oxide semiconductor
nanoclusters
nanocomposite
nanomagnetism
spintronics