Exchange Bias Studies in Core/Shell Structures Nanoparticles

ORAL

Abstract

This study is focused on a comparison of magnetic properties of chemically synthesized core/shell structured iron/iron-oxide nanoparticles with different core sizes and comparable shell thickness. Particles were synthesized by high temperature decomposition of iron organometallic compounds. Thermomagnetic data revealed that particles are superparamagnetic at room temperature. The field cooled hysteresis loops showed interesting features of enhanced coercivity and horizontal and vertical shifts along directions of the cooling field, all strongly depend on temperature, indicative of an exchange-bias-like phenomenon. These effects were more pronounced in smaller core size nanoparticles with an exchange bias field of 4098 Oe. The spin-glass-like phase with high-field irreversibility in the iron oxide shells played the role of the fixed phase in the core/shell system and provided the pinning force to the reversible spins. The magnetic domains and higher contributions from the surface anisotropy in the hollow nanoparticles caused enormous magnetic frustration that is the origin of high field irreversibility and vertical shift of hysteresis loop in these particles.

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Authors

  • Hafsa Khurshid

    University of South Florida

  • Sayan Chandra

    University of South Florida-Physics, University of South Florida

  • Wanfeng Li

    University of Delaware

  • M.H. Phan

    University of South Florida-Physics, University of South Florida

  • George Hadjipanayis

    Department of Physics and Astronomy, University of Delaware, Newark, DE, U.S.A., Department of Physics and Astronomy, University of DE, Newark, DE, 19711, USA, Department of Physics and Astronomy, University of DE, Newark, DE, 19716, USA, University of Delaware

  • H.S. Srikanth

    University of South Florida-Physics, University of South Florida, University of Delaware