J. Jorzick

Spin-wave quantization and dynamic coupling in micron-size circular magnetic dots

We report on the observation of spin-wave quantization in square arrays of micron-size circular magnetic Ni80Fe20 dots by means of Brillouin light-scattering spectroscopy. For a large wave-vector interval several discrete, dispersionless modes with a frequency splitting of up to 2.5 GHz were observed. The modes are identified as magnetostatic surface spin waves laterally quantized due to in-plane confinement in each single dot. The frequencies of the lowest observed modes decrease with increasing distance between the dots, thus indicating an essential dynamic magnetic dipole interaction between the dots at small interdot distances.

Spin wave quantization in laterally confined magnetic structures (invited)

An overview of the current status of the study of spin wave excitations in arrays of magnetic dots and wires is given. We describe both the status of theory and recent inelastic light scattering experiments addressing the most important issues; the quantization of localized spin waves due to the in-plane confinement of spin waves in elements, dipolar coupling between the quantized modes, and the localization of the modes within rectangular elements due to an inhomogeneous demagnetizing field.

Elastic properties of thin h-BN films investigated by Brillouin light scattering

Hexagonal BN films have been deposited by rf-magnetron sputtering with simultaneous ion plating. The elastic properties of the films grown on silicon substrates under identical coating conditions have been de-termined by Brillouin light scattering from thermally excited surface phonons. Four of the five independent elastic constants of the deposited material are found to be c11 = 65 GPa, c13 = 7 GPa, c33 = 92 GPa and c44 = 53 GPa exhibiting an elastic anisotropy c11/c33 of 0.7. The Youngs modulus determined with load indenta-tion is distinctly larger than the corresponding value taken from Brillouin light scattering. This discrepancy is attributed to the specific morphology of the material with nanocrystallites embedded in an amorphous matrix.

Spin-wave excitations in finite rectangular elements

Excitation spectrum of homogeneously magnetized Ni/sub 80/Fe/sub 20/ rectangles using Brillouin light scattering (BLS) is reported. A model to qualitatively describe the spin-wave spectrum is presented and its results is compared with both experiment and micromagnetic simulations. Micromagnetic simulation show that the internal field is inhomogeneous along the direction of the applied field. It was concluded that the spin wave modes can be approximately described as a linear combination of the modes of a longitudinally magnetized stripe and a transversely magnetized stripe.

Elastic properties of indium tin oxide films

The Brillouin light scattering (BLS) technique is used to observe thermally excited acoustic surface phonons in backscattering geometry. A series of DC sputtered ITO films with thicknesses ranging from 31 to 3600 nm were deposited at a substrate temperature of 1508C on hydrogen terminated (100) silicon. From the dispersion of the Rayleigh mode and of the higher order Rayleigh-like modes in the discrete part of the spectrum, three independent stiffness constants, c , c and c , are determined 11 33 55 with reasonable accuracy. These results are obtained using a hexagonal model, which takes the axial symmetry of the film material into account. The elastic anisotropy, c yc f5y4, is attributed to the single crystal anisotropy of the strongly textured ITO. The 11 33 Youngs moduli obtained from BLS and a microindentation analysis are in good agreement. 2001 Elsevier Science B.V. All rights reserved.

Brillouin light scattering study on the elastic properties of thick sputtered c-BN films

The Brillouin light scattering technique is used to observe thermally excited acoustic phonons in backscattering geometry in a transparent, 1.8 μm thick diode sputtered c-BN film. The Rayleigh mode at the film surface and the quasilongitudinal bulk mode were detected under various angles of light incidence. The angular dependent phase velocity of the bulk wave provides evidence for an elastic anisotropy of the film material. Complete descriptions of the elastic properties are presented, assuming either isotropic or hexagonal film symmetry. The reduction of the film stiffness in comparison to the single crystal and the origin of the elastic anisotropy of c11/c33≈4/5, where c11 and c33 are the respective extensional stiffness constants parallel and perpendicular to the film, is discussed. Both effects are predominantly caused by sp2-bonded material and a structured film growth.

Magneto-dipole coupling in arrays of micron-size rectangular magnetic elements

Static magnetic properties of arrays of micron-size rectangular magnetic permalloy elements are investigated by means of magneto-optic Kerr-effect magnetometry and magnetic force microscopy. The influence of the size and the spacing between the elements on the magnetization curves of the arrays is studied for different orientations of the applied magnetic field. A sizeable magnetic dipole coupling between the elements is found, affecting strongly the magnetic properties of the arrays.

Brillouin light scattering from surface phonons in hexagonal and cubic boron nitride films

Abstract Phase velocities of surface acoustic waves in several boron nitride films were investigated by Brillouin light scattering. In the case of films with a predominantly hexagonal crystal structure, grown under conditions close to the nucleation threshold of cubic BN, four independent elastic constants have been determined from the dispersion of the Rayleigh and the first Sezawa mode. The large elastic anisotropy of up to c11/c33=0.1 is attributed to a pronounced texture with the c-axes of the crystallites parallel to the film plane. In the case of cubic BN films, the dispersion of the Rayleigh wave provides evidence for the existence of a more compliant layer at the substrate-film interface. The observed broadening of the Rayleigh mode is identified to be caused by the film morphology.

Quantized spin wave modes in micron size magnetic disks

We report on the observation of spin wave quantization in tangentially magnetized Ni80Fe20 disks by means of Brillouin light scattering spectroscopy. For a large wave vector interval, several discrete, dispersionless modes with a frequency splitting up to 2.5 GHz were observed. The modes are identified as being magnetostatic surface spin wave modes quantized by their lateral confinement in the disk. For the lowest modes, dynamic magnetic dipolar coupling between the disks is found for a disk spacing of 0.1 μm.

Characterization of elastic properties of hard carbon and boron nitride films using the Brillouin light scattering technique

The elastic properties of thin graphitic carbon and hexagonal boron nitride films have been determined by Brillouin light scattering from thermally excited surface acoustic phonons. The carbon films have been grown by plasma beam deposition at 420°C. The BN films have been deposited by r.f.-magnetron sputtering and simultaneous ion plating. In the case of amorphous carbon a layered substructure has been found with a rather compliant intermediate layer at the interface. The stiffness of the films increases with increasing ion energy. As for carbon the BN coatings exhibit a pronounced elastic anisotropy indicating a preferred orientation of the hexagonal planes perpendicularly to the surface. The comparison of the Youngs moduli determined by load indentation and by Brillouin light scattering allows the conclusion that the material is composed of two or more components of different stiffness.