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

Journal Article · Mon Nov 18 00:00:00 EST 2013 · Physical Review. B, Condensed Matter and Materials Physics

DOI:https://doi.org/10.1103/PhysRevB.88.174415· OSTI ID:1133364

Roy, Beas ^[1]; Pandey, Abhishek ^[1]; Zhang, Qiang ^[1]; Heitmann, T. W. ^[2]; Vaknin, David ^[1]; Johnston, David C. ^[1]; Furukawa, Yuji ^[1]

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1. Ames Laboratory
2. University of Missouri

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.

• Research Organization: Ames Lab., Ames, IA (United States)
• Sponsoring Organization: USDOE Office of Science (SC)
• DOE Contract Number: DE-AC02-07CH11358
• OSTI ID: 1133364
• Report Number(s): IS-J 8207
• Journal Information: Physical Review. B, Condensed Matter and Materials Physics, Vol. 88; ISSN 1098-0121
• Publisher: American Physical Society (APS)
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE