Chemical Inhomogeneity and Mixed-State Ferromagnetism in Diluted Magnetic Semiconductor Co:TiO2

Journal Article · Tue Jan 01 00:00:00 EST 2008 · Chemistry of Materials

DOI:https://doi.org/10.1021/cm702089z· OSTI ID:959652

Ogale, S; Kundaliya, D; Mehraeen, S; Fu, L; Zhang, S; Lussier, A; Dvorak, J; Browning, N; Idzerda, Y; Venkatesan, T

Diluted magnetic semiconductors (DMS) are among the most intensely investigated materials in recent times in view of their great application potential. Yet, they are also the most controversial because of the possibility of extrinsic effects attributable to dopant solubility and clustering, point defects, incorporation of unintentional impurities, etc. This has highlighted the central role of materials chemistry in rendering a specific microstate and property response. In this work, we provide a combined window of high-resolution scanning transmission electron microscopy and electron energy-loss spectrometry, X-ray absorption (XAS)/X-ray magnetic circular dichroism (XMCD), and magnetization measurements on epitaxial rutile CoxTi1-xO2 (x = 0-0.06) system (the first discovered oxide-DMS, which continues to be controversial) grown at low temperature (400 C) under different ambient atmospheres. The study brings out a mixed-state scenario of ferromagnetism involving intrinsic DMS (uniform dopant distribution at low dopant concentration) and coupled cluster magnetism, involving cobalt associations within the matrix at higher concentrations. We also show that by matrix valence control during growth, it is possible to realize a uniform embedded cluster state and the related coupled cluster magnetism.

• Research Organization: Brookhaven National Lab. (BNL), Upton, NY (United States). National Synchrotron Light Source
• Sponsoring Organization: Doe - Office Of Science
• DOE Contract Number: DE-AC02-98CH10886
• OSTI ID: 959652
• Report Number(s): BNL-82638-2009-JA; CMATEX; TRN: US201016%%796
• Journal Information: Chemistry of Materials, Vol. 20; ISSN 0897-4756
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
ABSORPTION
CHEMISTRY
COBALT
DISTRIBUTION
ELECTRONS
FERROMAGNETISM
IMPURITIES
MAGNETIC CIRCULAR DICHROISM
MAGNETIC SEMICONDUCTORS
MAGNETISM
MAGNETIZATION
MIXED STATE
POINT DEFECTS
RUTILE
SOLUBILITY
SPECTROSCOPY
TRANSMISSION ELECTRON MICROSCOPY
VALENCE
national synchrotron light source