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Title: Experimental evidence of a collinear antiferromagnetic ordering in the frustrated CoAl2O4 spinel

Nuclear magnetic resonance (NMR), neutron diffraction (ND), x-ray diffraction, magnetic susceptibility χ, and specific-heat measurements on the frustrated A-site spinel CoAl2O4 compound reveal a collinear antiferromagnetic ordering below TN = 9.8(2) K. A high-quality powder sample characterized by x-ray diffraction that indicates a relatively low Co-Al inversion parameter x=0.057(20) in (Co1-xAlx)[Al2-xCox]O4, shows a broad maximum around 15 K in χ(T) and a sharp peak at TN in heat capacity Cp. The average-ordered magnetic moment of Co2+ (S=32) ions at the A site is estimated to be 2.4(1) μB from NMR and 1.9(5) μB from ND which are smaller than the expected value of 3 μB for S=32 and g = 2. Antiferromagnetic spin fluctuations and correlations in the paramagnetic state are revealed from the χ, NMR, and ND measurements, which are due to spin frustration and site inversion effects in the system. The ND data also show short-range dynamic magnetic ordering that persists to a temperature that is almost twice TN.
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  1. Ames Laboratory
  2. University of Missouri
Publication Date:
OSTI Identifier:
Report Number(s):
IS-J 8207
Journal ID: ISSN 1098-0121
DOE Contract Number:
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review. B, Condensed Matter and Materials Physics; Journal Volume: 88
American Physical Society (APS)
Research Org:
Ames Laboratory (AMES), Ames, IA (United States)
Sponsoring Org:
USDOE Office of Science (SC)
Country of Publication:
United States