We investigate voltage induced perpendicular magnetic anisotropy (PMA) changes in MgO/Cr/Au/Fe80Co20/MgO/polyimide/ indium tin oxide (ITO). In order to observe the PMA change, spin wave frequency was measured by Brillouin light scattering with finite bias voltages applied between Au and ITO electrodes. The obtained PMA constants from spin wave frequency of Fe80Co20 layer show clear bias voltage dependences, which agree well with the previous polar-Kerr effect measurement results and theoretical study. This study suggests spintronics devices operated by an electric field for next generation devices complying with low-power consumption.

We report Brillouin light scattering experiments on polymeric uniaxial Langmuir-Blodgett films, which have their preferred axis, the c axis, in the plane of the film. Both acoustic surface and bulk modes were observed. In addition to the usual Rayleigh and Sezawa film modes, a longitudinal guided acoustic phonon was identified. Also observed, and verified by computer simulations, was a resonant enhancement of the scattering cross section for some Sezawa modes due to an additional bulk coupling mechanism of the scattered light to the film modes. The complete set of elastic constants as well as the refractive indices were determined from the spectra. For the samples that we had measured, with more than ten molecular monolayers, the elastic constants do not depend on the film thickness. The ratio between the transverse and the longitudinal sound velocities is found to be much smaller than for ordinary solids.

In Brillouin-light-scattering studies of a series of Ag/Pd superlattice films we have observed scattering from longitudinal guided modes (LGMs) whose velocities are determined primarily by the en elastic constant. From the measured velocity of the first-order LGM, we have obtained the first accurate determination of CM for metallic thin films. For the Ag/Pd superlattice films, large increases in both the longitudinal (en) and shear (C55) elastic constants were observed as the superlattice modulation wavelength A was decreased below A -60 A.PACS numbers: 62.20. Dc, 62.30.+d, 68.60.Bs, 78.35,+c The elastic properties of metallic superlattice films have been shown to depend on the superlattice modulation wavelength A. 1_9 Dramatic enhancements of up to 500% in the biaxial modulus YB for A ^ 25 A were inferred from bulge tester measurements. 1 ' 2 More recently, Brillouin light scattering (BLS) has been used to study metallic superlattice films. 3 " 8 Changes of up to 20% in the Rayleigh mode velocity have been observed 3,8 as A was varied between 5 and 100 A.The elastic constants of metallic films can be determined from BLS measurements of the Rayleigh and Sezawa 4 " 6 film-guided acoustic-mode velocity dispersion. For sputtered films which have hexagonal symmetry, 8 the velocities of these modes are determined by four of the five independent elastic constants: en, C13, C33, and C55 -c^-For film thicknesses greater than 3000 A, the Rayleigh mode velocity is determined almost entirely by C55. 8 However, it is very difficult to distinguish the contributions of the other three elastic constants to the Sezawa mode velocities. 4 " 6,10 Because of this, in previous BLS studies, 4 " 6 two elastic constants were fixed to their average values and the remaining two elastic constants were obtained by using a least-squares-fitting procedure. Despite combining such fits to the measured mode velocities with comparisons of the measured and calculated scattering intensities, ambiguities in the elastic constant values were obtained. 10 In the present work, we report the first indentification of light scattering from the longitudinal guided modes (LGMs) of metallic films.LGMs are film-guided acoustic modes which have displacements primarily along the propagation direction in the film plane, and velocities that are strongly dependent on the longitudinal elastic constant c\\. In previous BLS studies, 11,12 LGMs were observed for films that were transparent to the light. For transparent films, strong LGM peaks are observed in the BLS spectra since the large penetration depth of the light £ 0 pt produces a large amount of elasto-optic scattering. 13 However, for metallic films, S opt (=150 A) is much smaller than for transparent films, so that the scattering intensity is due almost entirely to the surface ripple mechanism. 13 For semi-infinite metallic films, theLGMs become the longitudinal resonance, 14 there is no surface ripple, and a dip corresponding to the longitudinal resonance should be observed in BLS spectra. 14 However, ...