Exchange bias of ordered α-Fe2O3 nanowires: A first-order reversal curve analysis

Abstract

Ordered α-Fe2O3 nanowires with different gap sizes and diameters were fabricated using SBA-15 as template through varying calcination temperature. The composition, microstructure and morphology of the samples were characterized by XRD, TEM and N2 adsorption–desorption isotherms. The results showed that the α-Fe2O3 replicated the pore channels of SBA-15. The nanowire diameter and wire spacing were controllably changed at different calcination temperatures. ZFC-FC, hysteresis lines and First-order reversal curve (FORC) of the samples were tested at 10 K, 50 K, 100 K, 200 K and 300 K. Exchange bias (EB) was observed under low-temperature field cooling conditions due to the increase of spin disorder on the surface of small size α-Fe2O3 which was freezen into a spin-glass-like phase at low temperature. The influence of the domain states and interactions on EB of α-Fe2O3 were investigated using FORC. The mixed domain states were observed for small size samples at low temperatures. The excitation of EB at low temperatures was proven to be influenced by magnetic interactions.