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

• Published in: Journal of applied physics 2013-05, Vol.113 (17), p.17B531
• Main Authors: Krycka, K. L., Borchers, J. A., Laver, M., Salazar-Alvarez, G., López-Ortega, A., Estrader, M., Suriñach, S., Baró, M. D., Sort, J., Nogués, J.
• Format: Article
• Language: English
• ISSN: 0021-8979; 1089-7550; 1089-7550
• DOI: 10.1063/1.4801423

The magnetic responses of two nanoparticle systems comprised of Fe3O4/γ-Mn2O3 (soft ferrimagnetic, FM/hard FM) and Fe3O4/MnO/γ-Mn2O3 (soft FM/antiferromagnetic, AFM/hard FM) are compared, where the MnO serves to physically decouple the FM layers. Variation in the temperature and applied field allows for Small Angle Neutron Scattering (SANS) measurements of the magnetic moments both parallel and perpendicular to an applied field. Data for the bilayer particle indicate that the graded ferrimagnetic layers are coupled and respond to the field as a single unit. For the trilayer nanoparticles, magnetometry suggests a Curie temperature (TC) ≈ 40 K for the outer γ-Mn2O3 component, yet SANS reveals an increase in the magnetization associated with outer layer that is perpendicular to the applied field above TC during magnetic reversal. This result suggests that the γ-Mn2O3 magnetically reorients relative to the applied field as the temperature is increased above 40 K.