Cobalt Ferrite Films: Nano-polishing and Magnetic Properties

BILOVOL, V.; PAMPILLO, L. G.; MEIER, D.; WOLFF, U.; SACCONE, F. D.

IEEE TRANSACTIONS ON MAGNETICS

IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC

Lugar: New York; Año: 2014 vol. 50 p. 1 - 5

0018-9464

CoFe2O4 films were deposited on Si [(100) or (111)] substrates by pulsed laser deposition, varying substrate temperature and deposition time. All films showed highly (111)-preferred orientation. Magnetic measurements (hysteresis loops) at room temperature indicated that the films have in-plane magnetic anisotropy. By atomic force microscopy the surface topology revealed an average roughness of approximately 15 nm due to the presence of droplets. In order to define the relevance of droplets on the films? magnetic properties, we applied a nano-polishing technique after which the surfaces became notoriously smoother. As a consequence of this surface modification, we found that the hysteresis loops (measured again after nano-polishing) revealed changes in the magnetic response of the samples. The thinner films (t ≈ 50 nm) revealed waist-type hysteresis loops with diminished values of the coercive field, while the thickest film (t ≈ 100 nm) increased its coercive field without qualitative change in its loop shape. We attributed the altered magnetic response to different mechanisms that depend on sample thickness. For the thinner films, an additional anisotropy (to that existing in the plane) was induced after the nano-polishing procedure. For the thickest film, it was observed that differences are present after the elimination of the droplets, showing their important role in the magnetic response of the films