Enhancement of surface spin disorder in hollow NiFe$_{2}$O$_{4}$ nanoparticles

ORAL

Abstract

We present synthesis and magnetic properties of hollow NiFe$_{2}$O$_{4}$ nanoparticles from core (Ni$_{33}$Fe$_{67})$/shell (NiFe$_{2}$O$_{4})$ structure based on Kirkendall effect. Morphology of the particles can be varied from hollow to solid NiFe$_{2}$O$_{4}$ nanoparticles by varying the reaction temperature and time of initial core/shell structure. Particles with hollow morphology are expected to show larger surface spin disordered or spin glass phase due to the presence of additional inner surface in addition to the usual outer surface in nanoparticles. Field cooled hysteresis loops exhibit significantly large shift due to unidirectional anisotropy resulting from the additional inner along with outer surface spin glass interface in particles with hollow morphology compared to particles with non-hollow (or solid) morphology that have only outer spin glass shell coupled with ferromagnetic core. The enhancement in the surface anisotropy is also noticeable which leads to an increase in the blocking temperature of the particles with hollow morphology.

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Authors

  • Ghulam Jaffari

    Department of Physics and Astronomy, University of Delaware, Newark DE 19716, Department of Physics and Astronomy, University of Delaware, Newark, DE 19716, USA, Dept. of Physics and Astronomy, University of Delaware

  • Abdullah Ceylan

    Physics Engineering Department, Hacettepe University, Beytepe, Ankara 06800, Turkey

  • Chaoying Ni

    Department of Materials Science and Engineering, University of Delaware, Newark DE 19716

  • Syed Shah

    Department of Material Science and Engineering; Department of Physics and Astronomy, Univeristy of Delaware, Newark, DE 19716, USA,, Dept of Materials Science and Egineering, University of Delaware, Materails Science and Engineering, University of Delaware