Correlating material-specific layers and magnetic distributions within onion-like Fe3O4/MnO/gamma-Mn2O3 core/shell nanoparticles

Abstract

The magnetic responses of two nanoparticle systems comprised of Fe3O4=c-Mn2O3(softferrimagnetic, FM/hard FM) and Fe3O4=MnO=c-Mn2O3(soft FM=antiferromagnetic, AFM/hardFM) are compared, where the MnO serves to physically decouple the FM layers. Variation in thetemperature and applied field allows for Small Angle Neutron Scattering (SANS) measurements ofthe magnetic moments both parallel and perpendicular to an applied field. Data for the bilayerparticle indicate that the graded ferrimagnetic layers are coupled and respond to the field as a singleunit. For the trilayer nanoparticles, magnetometry suggests a Curie temperature (TC) 40 K for theouterc-Mn2O3component, yet SANS reveals an increase in the magnetization associated with outerlayer that is perpendicular to the applied field aboveTCduring magnetic reversal. This resultsuggests that thec-Mn2O3magnetically reorients relative to the applied field as the temperature isincreased above 40 K.