| AVS 62nd International Symposium & Exhibition | |
| Magnetic Interfaces and Nanostructures | Tuesday Sessions |
| Session MI-TuM |
| Session: | Oxides, Fluorides, and Spin Structures |
| Presenter: | Michael Lee, University of California, Davis |
| Authors: | M. Lee, University of California, Davis T. Wynn, University of California, Davis R.V. Chopdekar, University of California, Davis E. Folven, Norwegian University of Science and Technology J. Grepstad, Norwegian University of Science and Technology A. Scholl, Lawrence Berkeley National Laboratory (LBNL) A. Young, Lawrence Berkeley National Laboratory (LBNL) S. Retterer, Oak Ridge National Laboratory Y. Jia, University of California, Davis B. Li, University of California, Davis Y. Takamura, University of California, Davis |
| Correspondent: | Click to Email |
Future memory devices must achieve improved storage density, stability, and low power consumption. To this end La0.67Sr0.33MnO3 (LSMO) is a promising material due to the confluence of many scientifically interesting functional properties, including ferromagnetism, colossal magnetoresistance, and high spin-polarization. The ability to tune these properties through a number of different stimuli is equally encouraging. In order to utilize LSMO the magnetic behavior of nanostructures must be well characterized, but due to the vast array of energetically competitive interactions present, size effects play a significant role in oxide nanostructures.
In this work we investigated the evolution of domain structure as a function of temperature in micromagnets patterned into epitaxial films of LSMO via x-ray photoemission electron microscopy (XPEEM). Results showed transitions from vortex to Landau patterns in circular patterns (2μm in diameter) indicating that saturation magnetization and magnetocrystalline anisotropy (K1) have different dependence on temperature. Additionally, squares (also 2μm) with edges aligned along the hard magnetization axis began in the Landau state dictated by shape anisotropy, but developed distinct inner and outer flux closure structures as K1 becomes stronger at lower temperatures. This could mean the creation of magnetic domain structures in devices that have more fine-tuned and efficient behavior. The presence of these novel spin-textures has been used to extract approximate fundamental magnetic parameters for LSMO at micro- and nano-dimensions. We have developed a method to extract values of K1 from simulations of the observed XPEEM images. Parameters obtained from circular micromagnets were used to simulate other experimentally observed magnetic domain structures and confirm the validity of the procedure. This is a new analysis technique making it possible to locally measure magnetic properties in structures that would otherwise be difficult or impossible to characterize.
Novel spin-textures have been observed as a direct result of studying materials systems that express magnetocrystalline anisotropy. Using the newly developed technique, approximate values of magnetocrystalline anisotropy have been uncovered for the micromagnets studied to more clearly describe the magnetic behavior of LSMO nanostructures. The outcome of this project will improve the quality of future research due to a deeper understanding of the delicate balance of energies.