| AVS 54th International Symposium | |
| Magnetic Interfaces and Nanostructures | Wednesday Sessions |
| Session MI-WeA |
| Session: | Nanomagnetic Imaging and Spectroscopy |
| Presenter: | R. Proksch, Asylum Research |
| Authors: | S.V. Kalinin, Oak Ridge National Laboratory S. Jesse, Oak Ridge National Laboratory R. Proksch, Asylum Research |
| Correspondent: | Click to Email |
Dissipative dynamics in magnetic materials and nanostructures is directly related to the physics of wall pinning mechanisms and spin-lattice interactions. Understanding these mechanisms on the level of a single pinning center (e.g. dislocation, second phase inclusion, or other micro-structural element) is crucial for progress in magnetic device applications. Here, we report quantitative mapping of magnetic dissipation on a single defect center in single-crystal yttrium-iron garnet (YIG). The image formation mechanism in Magnetic Dissipation Force Microscopy is analyzed in detail, and it is shown that small frequency dispersion in the cantilever transfer function leads to qualitative errors if the Cleveland formula is used. This leads to cross-talk between the domain pattern and dissipation image. The correction algorithms based on (a) direct transfer function calibration and (b) statistical image analysis are suggested. To decouple the dissipation and force gradient signal, we have developed a novel excitation approach in SPM based on an excitation signal having a finite density in a frequency band in the Fourier domain. This band excitation method allows very rapid acquisition of the full frequency response at each point in an image and in particular enables the direct measurement of energy dissipation through the determination of the Q-factor of the cantilever-sample system. The use of standard MDFM and BE-MFM illustrated the presence of ring-type dissipation contrast associated with single defect centers, corresponding to energy loss of ~1 eV/oscillation. The distance dependence of the ring diameter suggests that the dissipation is resonant in nature and corresponds to well defined field magnitude. The crystallographic origins of the defects are analyzed. Similar contrast is observed in other nanomagnetic systems including nanocrystalline iron, and magnetic nanoparticles from magnetotactic bacteria. Research was sponsored by the Division of Materials Sciences and Engineering, Office of Basic Energy Sciences, U.S. Department of Energy at Oak Ridge National Laboratory, managed and operated by UT-Battelle, LLC.