Exchange bias and Verwey transition in Fe5C2/Fe3O4 core/shell nanoparticles

This report presents new findings of exchange bias and related structural and magnetic properties in iron carbide/magnetite (Fe5C2/Fe3O4) core/shell nanoparticles. The exchange bias emerges from an energetic landscape, namely a first-order phase transition-the Verwey transition at 125 K, during which the Fe3O4 shell changes from the cubic to monoclinic structure. The phase transition leads to the exchange bias because it results in abrupt changes in magnetocrystalline anisotropy and exchange coupling. Another unique phenomenon identified in this composite system is enhanced magnetic coercivity due to the uniaxial anisotropy of the monoclinic phase. An analysis of the correlations between the observed phenomena is given based on the temperature dependence of the coercivity, the exchange bias field values, and the Verwey transition temperature.

Automated summary

New findings of exchange bias and enhanced magnetic coercivity were reported in iron carbide/magnetite core/shell nanoparticles, attributed to the structural changes during the Verwey transition of the Fe3O4 shell and the uniaxial anisotropy of the monoclinic phase.