Regensburg 2022 – wissenschaftliches Programm

Bereiche | Tage | Auswahl | Suche | Aktualisierungen | Downloads | Hilfe

MA: Fachverband Magnetismus

MA 19: Poster 1

MA 19.64: Poster

Dienstag, 6. September 2022, 17:30–20:00, P2

Structure and magnetism of hematite nanodiscs — •Maryna Spasova and Michael Farle — Faculty of Physics and Center of Nanointegration (CENIDE), University of Duisburg-Essen, Germany

Hexagonal shaped, single crystal hematite nanodiscs with thickness of 20 nm and different lateral sizes from 110 nm up to 250 nm were synthesized by an alcohol-thermal reaction. High Resolution Transmission Electron Microscopy reveals a very high crystallinity with (0001) basal planes and (101-2) side surfaces. The temperature of the Morin transition (MT) decreases for smaller diameters of the nanodiscs. The magnetization above the MT, however, does not depend on the particle size. It is close to the bulk value (M = 0.3 Am2/kg) whereas the coercivity decreases with increasing diameter from 55 kA/m (110 nm) to 37 kA/m (250 nm). Below the MT the nanodiscs are ferromagnetic r due to uncompensated surface magnetic moments which are perpendicular to the (0001) crystal plane. The magnetization measured at 10K is proportional to the surface area of the sample. The coercivity at 10 K increases with increasing particle diameter, i.e. 50 kA/m for 110 nm up to 550 kA/m for 250 nm. A very high irreversibility field of 3000 kA/m indicates a high magnetic anisotropy of the sample.