Monodispersed MnO nanoparticles with epitaxial Mn3O4 shells

A. E. Berkowitz; G. F. Rodriguez; J. I. Hong; K. An; T. Hyeon; N. Agarwal; David Smith; E. E. Fullerton

doi:10.1088/0022-3727/41/13/134007

Monodispersed MnO nanoparticles with epitaxial Mn₃O₄ shells

A. E. Berkowitz, G. F. Rodriguez, J. I. Hong, K. An, T. Hyeon, N. Agarwal, David Smith, E. E. Fullerton

Research output: Contribution to journal › Article › peer-review

34 Scopus citations

Abstract

We report the microstructural and magnetic properties of monodispersed nanoparticles (NPs) of antiferromagnetic MnO (T_N = 118 K), with epitaxial ferrimagnetic Mn₃O₄ (T_C = 43 K) shells. Above T_C, an unusually large magnetization is present, produced by the uncompensated spins (UCSs) on the surface of the MnO particles. These spins impart a net anisotropy to the MnO particles that is approximately three orders of magnitude larger than the bulk value. As a result, an anomalously high blocking temperature is exhibited by the MnO particles, and finite coercivity and exchange bias are present above T_C. When field cooled below T_C, a strong exchange bias was established in the Mn₃O₄ shells as a result of high net anisotropy of the MnO particles. A large coercivity was also observed. Models of several aspects of the behaviour of this unusual system emphasized the essential role of the UCSs on the surfaces of the MnO NPs.

Original language	English (US)
Article number	134007
Journal	Journal of Physics D: Applied Physics
Volume	41
Issue number	13
DOIs	https://doi.org/10.1088/0022-3727/41/13/134007
State	Published - Jul 7 2008

ASJC Scopus subject areas

Electronic, Optical and Magnetic Materials
Condensed Matter Physics
Acoustics and Ultrasonics
Surfaces, Coatings and Films

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10.1088/0022-3727/41/13/134007

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title = "Monodispersed MnO nanoparticles with epitaxial Mn3O4 shells",

abstract = "We report the microstructural and magnetic properties of monodispersed nanoparticles (NPs) of antiferromagnetic MnO (TN = 118 K), with epitaxial ferrimagnetic Mn3O4 (TC = 43 K) shells. Above TC, an unusually large magnetization is present, produced by the uncompensated spins (UCSs) on the surface of the MnO particles. These spins impart a net anisotropy to the MnO particles that is approximately three orders of magnitude larger than the bulk value. As a result, an anomalously high blocking temperature is exhibited by the MnO particles, and finite coercivity and exchange bias are present above TC. When field cooled below TC, a strong exchange bias was established in the Mn3O4 shells as a result of high net anisotropy of the MnO particles. A large coercivity was also observed. Models of several aspects of the behaviour of this unusual system emphasized the essential role of the UCSs on the surfaces of the MnO NPs.",

author = "Berkowitz, {A. E.} and Rodriguez, {G. F.} and Hong, {J. I.} and K. An and T. Hyeon and N. Agarwal and David Smith and Fullerton, {E. E.}",

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AU - Berkowitz, A. E.

AU - Rodriguez, G. F.

AU - Hong, J. I.

AU - An, K.

AU - Hyeon, T.

AU - Agarwal, N.

AU - Smith, David

AU - Fullerton, E. E.

PY - 2008/7/7

Y1 - 2008/7/7

N2 - We report the microstructural and magnetic properties of monodispersed nanoparticles (NPs) of antiferromagnetic MnO (TN = 118 K), with epitaxial ferrimagnetic Mn3O4 (TC = 43 K) shells. Above TC, an unusually large magnetization is present, produced by the uncompensated spins (UCSs) on the surface of the MnO particles. These spins impart a net anisotropy to the MnO particles that is approximately three orders of magnitude larger than the bulk value. As a result, an anomalously high blocking temperature is exhibited by the MnO particles, and finite coercivity and exchange bias are present above TC. When field cooled below TC, a strong exchange bias was established in the Mn3O4 shells as a result of high net anisotropy of the MnO particles. A large coercivity was also observed. Models of several aspects of the behaviour of this unusual system emphasized the essential role of the UCSs on the surfaces of the MnO NPs.

AB - We report the microstructural and magnetic properties of monodispersed nanoparticles (NPs) of antiferromagnetic MnO (TN = 118 K), with epitaxial ferrimagnetic Mn3O4 (TC = 43 K) shells. Above TC, an unusually large magnetization is present, produced by the uncompensated spins (UCSs) on the surface of the MnO particles. These spins impart a net anisotropy to the MnO particles that is approximately three orders of magnitude larger than the bulk value. As a result, an anomalously high blocking temperature is exhibited by the MnO particles, and finite coercivity and exchange bias are present above TC. When field cooled below TC, a strong exchange bias was established in the Mn3O4 shells as a result of high net anisotropy of the MnO particles. A large coercivity was also observed. Models of several aspects of the behaviour of this unusual system emphasized the essential role of the UCSs on the surfaces of the MnO NPs.

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Monodispersed MnO nanoparticles with epitaxial Mn₃O₄ shells

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