Antiferromagnetic Order in MnO Spherical Nanoparticles

Wang, C.H.; Baker, G.A.; Christianson, A.D.; Nagler, S.E.; Deen, P.D.; Baker, S.N.; Lumsden, M.D.; Su, Y.; Heller, W.T.; Cranswick, L.M.D.

doi:10.1103/PhysRevB.83.214418

Journal Article

Antiferromagnetic Order in MnO Spherical Nanoparticles

Wang, C. H. ; Baker, S. N. ; Lumsden, M. D. ; Nagler, S. E. ; Heller, W. T. ; Baker, G. A. ; Deen, P. D. ; Cranswick, L. M. D. ; Su, Y.FZJ* ; Christianson, A. D.FZJ*

2011
APS College Park, Md.

Physical review / B 83(21), 214418 (2011) [10.1103/PhysRevB.83.214418]

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Please use a persistent id in citations: http://hdl.handle.net/2128/10932 doi:10.1103/PhysRevB.83.214418

Abstract: We have performed unpolarized and polarized neutron diffraction experiments on monodisperse 8- and 13-nm antiferromagnetic MnO nanoparticles. For the 8-nm sample, the antiferromagnetic transition temperature T-N (114 K) is suppressed compared to that in the bulk material (119 K), while for the 13-nm sample T-N (120 K) is comparable to that in the bulk. The neutron diffraction data of the nanoparticles is well described using the bulk MnO magnetic structure but with a substantially reduced average magnetic moment of 4.2 +/- 0.3 mu(B)/Mn for the 8-nm sample and 3.9 +/- 0.2 mu(B)/Mn for the 13-nm sample. An analysis of the polarized neutron data on both samples shows that in an individual MnO nanoparticle about 80% of Mn ions order. These results can be explained by a structure in which the monodisperse nanoparticles studied here have a core that behaves similar to the bulk with a surface layer which does not contribute significantly to the magnetic order.

Keyword(s): Magnetic Materials (1st) ; Key Technologies (1st) ; Magnetism (2nd) ; J

Classification:

Physics, Condensed Matter

Note: We acknowledge useful discussions with J. Musfeldt and I. Swainson. Research Work at ORNL was sponsored by the Laboratory Directed Research and Development Program of ORNL, and was supported by the Scientific User Facilities Division Office of Basic Energy Sciences, DOE. A portion of this research was conducted at the Center for Nanophase Materials Sciences, which is sponsored at ORNL by the Office of Basic Energy Sciences, US DOE.

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