Browsing by Author "Wuttig, Manfred"

Now showing 1 - 5 of 5
  • Thumbnail Image
    Destruction of spin cycloid in (111)(c)-oriented BiFeO3 thin films by epitiaxial constraint: Enhanced polarization and release of latent magnetization
    Bai, Feiming; Wang, Junling; Wuttig, Manfred; Li, Jiefang; Wang, Naigang; Pyatakov, Alexander P.; Zvezdin, Anatoly Konstantinovich; Cross, L. E.; Viehland, Dwight D. (AIP Publishing, 2005-01-01)
    In BiFeO3 films, it has been found that epitaxial constraint results in the destruction of a space modulated spin structure. For (111)c films, relative to corresponding bulk crystals, it is shown (i) that the induced magnetization is enhanced at low applied fields; (ii) that the polarization is dramatically enhanced; whereas, (iii) the lattice structure for (111)(c) films and crystals is nearly identical. Our results evidence that eptiaxial constraint induces a transition between cycloidal and homogeneous anti ferromagnetic spin states, releasing a latent antiferromagnetic component locked within the cycloid. (C) 2005 American Institute of Physics.
  • Thumbnail Image
    Dramatically enhanced polarization in (001), (101), and (111) BiFeO3 thin films due to epitiaxial-induced transitions
    Li, Jiefang; Wang, Junling; Wuttig, Manfred; Ramesh, R.; Wang, Naigang; Ruette, Benjamin; Pyatakov, Alexander P.; Zvezdin, Anatoly Konstantinovich; Viehland, Dwight D. (AIP Publishing, 2004-06-01)
    Dramatically enhanced polarization has been found for (001), (101), and (111) films, relative to that of BiFeO3 crystals. The easy axis of spontaneous polarization lies close to (111), for the various oriented films. BiFeO3 films grown on (111) have a rhombohedral structure, identical to that of single crystals; whereas films grown on (101) or (001) are monoclinically distorted from the rhombohedral structure, due to the epitaxial constraint. (C) 2004 American Institute of Physics.
  • Thumbnail Image
    Magnetoelectric effect in sputtered composites
    Stein, Simon; Wuttig, Manfred; Viehland, Dwight D.; Quandt, Eckhard (American Institute of Physics, 2005-05-15)
    The magnetoelectric effect in millimeter size PMN-PT/Terfenol-D composites is known. In an effort towards miniaturization, we report on the magnetoelectric effect in micrometer-size sputtered composites. Multilayers of TbFe/FeCo with a thickness of 4 Am were sputter deposited on both sides of PMN-PT piezoelectric single crystals. The magnetoelectric voltage of samples was measured and reached values of 13 mV / (Oe cm) at dc bias fields of 2 mT, a linear dependence of magnetoelectric voltage on ac amplitude was detected in the range from 1 mT to 1 nT. (c) 2005 American Institute of Physics.
  • Thumbnail Image
    Origin of magnetic and magnetoelastic tweedlike precursor modulations in ferroic materials
    Saxena, A.; Castan, T.; Planes, A.; Porta, Micaela; Kishi, Y.; Lograsso, Thomas A.; Viehland, Dwight D.; Wuttig, Manfred; De Graef, M. (American Physical Society, 2004-05-14)
    Based on experimental observations of modulated magnetic patterns in a Co(0.5)Ni(0.205)Ga(0.295) alloy, we propose a model to describe a ( purely) magnetic tweed and a magnetoelastic tweed. The former arises above the Curie (or Neel) temperature due to magnetic disorder. The latter results from compositional fluctuations coupling to strain and then to magnetism through the magnetoelastic interaction above the structural transition temperature. We discuss the origin of purely magnetic and magnetoelastic precursor modulations and their experimental thermodynamic signatures.
  • Thumbnail Image
    Structural studies of Fe0.81Ga0.19 by reciprocal space mapping
    Viehland, Dwight D.; Li, Jiefang; Lograsso, Thomas A.; Ross, A.; Wuttig, Manfred (AIP Publishing, 2002-10-01)
    Reciprocal lattice mapping has been performed on Fe0.81Ga0.19 crystals by omega-omega/2theta, Psi-phi, and omega-phi scans. A strong elongation of the <001>(c) peak was found along the <110>(c) direction. omega scans revealed short lateral correlation lengths xi along <110>(c) and strong diffuse scattering along the <001>(c). Multiple domains with monoclinic symmetry (angle similar to190degrees) were observed by Psi-phi and omega-phi scans on the (001)(c) face, and were also tilted with respect to each other. The results show an average cubic structure with orthorhombic structural modulations, and two structural domain states that result in a limiting monoclinic symmetry. (C) 2002 American Institute of Physics.