Tuning the Magnetic Domain Structure of Spin-polarized Complex Oxide Nanostructures
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1256-N13-03
Tuning the Magnetic Domain Structure of Spin-polarized Complex Oxide Nanostructures Joanna S. Bettinger1,2,*; Rajesh V. Chopdekar1; Brooke. L. Mesler3,4; Douglas Chain1; Andrew Doran5; Erik Anderson4; Andreas Scholl5; Yuri Suzuki1,2 1. Department of Materials Science and Engineering, UC Berkeley, CA 94720, USA 2. Materials Sciences Division, Lawrence Berkeley Natl. Laboratory, Berkeley, CA 94720, USA 3. Applied Science and Technology, UC Berkeley, CA, USA 4. Center for X-ray Optics, Lawrence Berkeley Natl. Laboratory, Berkeley, CA 94720, USA 5. Advanced Light Source, Lawrence Berkeley Natl. Laboratory, Berkeley, CA 94720, USA * Presently at Stanford Synchrotron Radiation Laboratory, SLAC National Accelerator Laboratory, Menlo Park, CA 94025, USA ABSTRACT To successfully incorporate the highly spin-polarized material La0.7Sr0.3MnO3 (LSMO) into spin-based electronic devices it is essential to be able to control and tune the magnetic domain structure. In this work, we geometrically confine epitaxial thin films of LSMO into hexagons to examine the effect of magnetostatic and magnetic anisotropy energies on the domain formation. We find through careful choice of hexagon aspect ratio, crystalline direction, and substrate orientation, we can tune the magnetic domain formation to be single, two, six (flux closure), or other domain configurations. INTRODUCTION La0.7Sr0.3MnO3 (LSMO) is an important material from both the scientific as well as technological perspective. It is in the family of colossal magneto-resistive materials and undergoes a metal-insulator electronic transition near its Curie temperature (Tc).1 Below its Tc, the magnetic ground state is described by the double exchange mechanism; in double exchange, an electron can easily hop among Mn3+ and Mn4+ cations, so long as the Mn t2g core spins, whose interactions are mediated by oxygen anions, are parallel to one another. It has also been predicted to be half-metallic and thus an excellent candidate for spin-polarized memory devices. In order to incorporate LSMO into spin-based memory devices, we must understand the role of various magnetic anisotropies in determining the domain state of the material. Domain structure involves a balance of shape, exchange, magnetostatic, magnetocrystalline, and magnetoelastic energies. LSMO films deposited on SrTiO3 (STO) substrates are under tensile strain, and their magnetic properties are affected by strain and magnetocrystalline effects.2,3,4,5 Geometrical confinement has been shown to affect the electronic and magnetic properties of LSMO. For instance, quasi-one-dimensional LSMO nanospheres (~90 nm) display a lower metal to insulator transition temperature and increased magnetoresistance.6 Patterned LSMO nanostructures show a magnetic domain pattern quite different from unpatterned films.7,8 Previously, Takamura et al.7 developed a technique in which LSMO nanostructures are defined in a nonmagnetic matrix. Photolithography techniques are used to define the ferromagnetic nanostructures, which are protected by res
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