skip to main content

DOE PAGESDOE PAGES

This content will become publicly available on February 23, 2018

Title: Enhanced Magnetization of Cobalt Defect Clusters Embedded in TiO 2-δ Films

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 TiO 2-δ films, producing an inhomogeneous magnetic moment, with certain regions producing over 2.5 μ B per Co, depending on the local dopant concentration. Polarized neutron reflectometry was used to depth-profile the magnetization in the Co:TiO 2-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 Co 0, with a minor fraction of Co 2+. The detected magnetizations have seldom been reported before and lie near the upper limit set by Hund’s rules for Co 0, 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 promotedmore » 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.« less
Authors:
ORCiD logo [1] ;  [2] ;  [2] ;  [3] ;  [4] ; ORCiD logo [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)
Publication Date:
Report Number(s):
BNL-114234-2017-JA
Journal ID: ISSN 1944-8244; TRN: US1702012
Grant/Contract Number:
SC0012704
Type:
Accepted Manuscript
Journal Name:
ACS Applied Materials and Interfaces
Additional Journal Information:
Journal Volume: 9; Journal Issue: 10; Journal ID: ISSN 1944-8244
Publisher:
American Chemical Society (ACS)
Research Org:
Brookhaven National Laboratory (BNL), Upton, NY (United States)
Sponsoring Org:
USDOE Office of Science (SC), Nuclear Physics (NP) (SC-26)
Country of Publication:
United States
Language:
English
Subject:
73 NUCLEAR PHYSICS AND RADIATION PHYSICS; nanoclusters; nanomagnetism; spintronics; dilute magnetic oxide semiconductor; nanocomposite
OSTI Identifier:
1389242