- Oscillatory surface in-plane lattice spacing during growth of Co and Cu on a Cu(001) single crystal (1995)
- Structural relaxation and magnetic anisotropies in Co/Cu(001) films (1996)
- The magnetic anisotropy of Co/Cu~001! films has been investigated by the magneto-optical Kerr effect, both in the pseudomorphic growth regime and above the critical thickness where strain relaxation sets in. A clear correlation between the onset of strain relaxation as measured by means of reflection high-energy electron diffraction and changes of the magnetic anisotropy has been found.
- Magnetic exchange coupling effects in asymmetric trilayer structures of MBE grown Co/Cr/Fe (1996)
- We present results of anisotropy and exchange-coupling studies of asymmetric Co/Cr/Fe trilayers and superlattices grown by molecular beam epitaxy on Cr~001!/Mg~001! buffers and substrates. The magnetic properties have been investigated using both the longitudinal magneto-optical Kerr effect and ferromagnetic resonance. The hysteresis data obtained from the trilayer system were fit to a theoretical model which contains both bilinear and biquadratic coupling. The effective in-plane anisotropy was found to be of fourfold symmetry with the same easy-axis orientation for both the Fe and Co layers. An analysis of the easy-axis hysteresis loops indicates long-period oscillatory coupling and also suggests a short periodic coupling. We show that weakly antiferromagnetically coupled asymmetric films might serve as potential candidates for improved spin-valve systems.
- Suppression of the magnetocrystalline bulk anisotropy in thin epitaxial Co(110) films on Cu(110) (1996)
- We report on an unexpected suppression of the magnetocrystalline anisotropy contribution in epitaxial fcc Co(110) films on Cu(110) below a thickness of dc=(50 +/- 10) Å. For film thicknesses larger than dc the measured anisotropy value agrees with published data. Measurements on films with reduced strain indicate a large strain dependence of dc . A model calculation based on a crystal-field formalism and discussed within the context of band theory, which explicitly takes tetragonal misfit strains into account, reproduces the experimen-tally observed anomalies. Our results indicate that the usually applied phenomenological description of anisotropies, assuming additive free energy terms for each anisotropy contribution, fails in this case.
- Brillouin light scattering investigations of exchange biased (110)-oriented NiFe/FeMn bilayers (1997)
- All contributing magnetic anisotropies in (110)-oriented exchange biased Ni 80 Fe 20 /Fe 50 Mn 50 double layers prepared by molecular beam epitaxy on Cu(110) single crystals have been determined by means of Brillouin light scattering. Upon covering the Ni 80 Fe 20 films by Fe 50 Mn 50 , a unidirectional anisotropy contribution appears, which is consistent with the measured exchange bias field. The uniaxial and fourfold in-plane anisotropy contributions are largely modified by an amount, which scales with the Ni 80 Fe 20 thickness, indicating an interface effect. The strong uniaxial anisotropy contribution shows an in-plane switching of the easy axis from  to  with increasing Ni 80 Fe 20 -layer thickness. The large mode width of the spin wave excitations, which exceeds the linewidth of uncovered Ni 80 Fe 20 films by a factor of more than six, indicates large spatial variations of the exchange coupling constant. (C) 1998 American Institute of Physics.
- Absence of elastic anomalies for Co/ Ni superlattices with oscillatory transport (1997)
- We report on Brillouin light scattering investigations of the elastic properties in Co/Ni superlattices which exhibit localized electronic eigenstates near the Fermi level causing an oscillation of the resistivity as a function of the superlattice periodicity A. No oscillations of the Rayleigh and Sezawa mode as a function of A could be observed within an error margin of +- 2% indicating that the localized electronic states do not contribute to the elastic constants.
- Anisotropic magnetic coupling of permalloy micron dots forming a square lattice (1997)
- Static magnetic and spin wave properties of square lattices of permalloy micron dots with thicknesses of 500 Å and 1000 Å and with varying dot separations have been investigated. A magnetic fourfold anisotropy was found for the lattice with dot diameters of 1 micrometer and a dot separation of 0.1 micrometer. The anisotropy is attributed to an anisotropic dipole-dipole interaction between magnetically unsaturated parts of the dots. The anisotropy strength (order of 100000 erg/cm^3 ) decreases with increasing in-plane applied magnetic field.
- Static and dynamic properties of patterned magnetic permalloy films (1997)
- Static magnetic and spin wave properties of square lattices of permalloy micron dots with thicknesses of 500 Å and 1000 Å and with varying dot separations have been investigated. The spin wave frequencies can be well described taking into account the demagnetization factor of each single dot. A magnetic four-fold anisotropy was found for the lattice with dot diameters of 1 micrometer and a dot separation of 0.1 micrometer. The anisotropy is attributed to an anisotropic dipole-dipole interaction between magnetically unsaturated parts of the dots. The anisotropy strength (order of 100000 erg/cm^3 ) decreases with increasing in-plane applied magnetic field.
- Propagation of linear and nonlinear spin wave excitations in YIG and LuBiFeO films studied by space resolved Brillouin light scattering (extended abstract) (1997)
- Spin waves and magnetic anisotropy in ultrathin (111)-oriented cubic films (1998)
- The dispersions of dipolar (Damon-Eshbach modes) and exchange dominated spin waves are calculated for in-plane magnetized thin and ultrathin cubic films with (111) crystal orientation and the results are compared with those obtained for the other principal planes. The properties of these magnetic excitations are examined from the point of view of Brillouin light scattering experiments. Attention is paid to study the spin-wave frequency variation as a function of the magnetization direction in the film plane for different film thicknesses. Interface anisotropies and the bulk magnetocrystalline anisotropy are considered in the calculation. A quantitative comparison between an analytical expression obtained in the limit of small film thickness and wave vector and the full numerical calculation is given.