AVS 52nd International Symposium
    Magnetic Interfaces and Nanostructures Wednesday Sessions
       Session MI-WeM

Paper MI-WeM4
A Comparative Study of the Magnetic Domain Structure of Mn Doped ITO Thin Films by Magnetic Force Microscopy

Wednesday, November 2, 2005, 9:20 am, Room 204

Session: Magnetic Imaging and Spectroscopies
Presenter: B.I. Kim, Boise State University
Authors: B.I. Kim, Boise State University
J.O. Holmes, Boise State University
M.R. Kongara, Boise State University
A. Punnoose, Boise State University
Correspondent: Click to Email
Semiconducting Mn doped ITO thin films have been studied with different Mn doping levels using high resolution magnetic force microscopy (MFM) to understand the magnetic microstructure and uniformity of this room temperature ferromagnet. The film was prepared by sol-gel mediated spin coat technique, and the Co-coated tip (radius < 10 nm) was magnetized vertically using strong external magnetic field before the experiment. We collected four different MFM images (topographic image, magnetic force image, amplitude image and phase image) at the same time to obtain complementary information using ac mode MFM technique. Stable imaging condition could be achieved at distance 50 -100 nm between tip and sample. The magnetic domain structures observed in the ambient condition show thin labyrinthine features with 1-2 µm width for all Mn : ITO thin films regardless of the Mn doping level. MFM images also show that magnetic structures are connected differently depending on the Mn concentration. We could observe a reproducible image with small fine magnetic features with 10nm size for the repeated images, indicating the fine features comes from 8 nm ferromagnetic nanoparticles confirmed from TEM. The sectional profiles across magnetic domains indicate that the variation between positive and negative orientation for the 6% Mn doped samples is twice bigger than those at 9% and 3% doped magnetic films, consistent with an independent magnetization measurement. Comparison of magnetic phase images with those of longitudinal medium suggests that the magnetic moments of Mn : ITO orient vertically on the plane of film surfaces. The study indicates the amount of Mn doping influences the individual magnetic fine features as well as the connectivity of magnetic domains. These observed domain features suggest that magnetic structures on nano- and- macro- scale of Mn : ITO films are closely related to the amount of Mn doping and preparation condition.