We provide an overview on the microscopic theory of Gilbert damping and a theoretical framework to calculate the damping constant. In general, the damping constant can be expressed using the spin susceptibility of electronic system using the molecular field Hamiltonian. For a uniform magnetic dynamics (Kittel mode), magnetic damping does not occur unless the magnetic scatterings or spin-orbit interactions exist. Based on these concepts, we have performed the first principles calculation for the Gilbert damping constants α of transition metal systems such as Fe-Ni and Fe-Pt using the tight-binding linear muffin-tin orbital (TB-LMTO) method with inclusion of spin-orbit interactions. Quantitatively, the calculated α's are approximately half of the experimental values, whereas the variations in the Fermi level dependence of α are much larger than these discrepancies. As expected, we confirm that for (Fe-Ni)_{1_X}Pt_X and FePt systems the Pt atoms enhance α due to their large spin-orbit coupling. For the disordered alloys, we find that α decreases with an increasing chemical degree of order in the wide range.

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  Enhancement of the longitudinal Kerr effect by excitation of surface plasmon resonance (SPR) in ferromagnetic Co₇₂Fe₈B₂₀/Au stacked films was investigated in a Kretschmann configuration with p-polarized light at 633 nm. We found that (1) it was possible to excite SPR in the bi-layer structure of Co₇₂Fe₈B₂₀/Au with the necessity of the Au layer faced to air. We also found that (2) the dependence of the longitudinal Kerr effect on the incident angle indicated that the saturation component of ellipticity was bell-shaped in the hysteresis loop, while the rotation angle had a dispersed-shaped distribution. In contrast, the rotation angle was bell-shaped for the linear component, while the ellipticity had a dispersed-shaped distribution. Moreover, we discovered that (3) the saturation component of the longitudinal Kerr effect in the Co₇₂Fe₈B₂₀/Au (20 nm) stacked film had a steep maximum as a function of the thickness of the ferromagnetic layer, and that the strongest resonance occurred at a ferromagnetic layer thickness of 8 nm. In addition, we found that (4) the linear component of the longitudinal Kerr effect was caused by the Faraday effect of the prism and glass substrate, which was extremely enhanced by SPR.

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  FePd-alloy thin films of 40 nm thickness are prepared on MgO single-crystal substrates of (001), (110), and (111) orientations by employing a two-step method consisting of deposition at a low temperature of 200 °C followed by annealing at a higher temperature in a range from 300 to 600 °C. The influences of substrate orientation and annealing temperature on the ordered phase formation and the surface roughness are investigated. FePd films with disordered A1 structure grow epitaxially on MgO substrates of all the orientations at 200 °C. Transformation from A1 to L1₀ phase starts to be observed in FePd films formed on the respective MgO substrates after annealing at 300, 500, and 600 °C. With increasing the annealing temperature up to 600 °C, the order degrees of FePd films formed on MgO substrates of (001), (110), and (111) orientations respectively increase to 0.63, 0.29, and 0.33. The films before annealing have very flat surfaces and the flat surfaces are kept after annealing for all the substrate orientations and the investigated annealing temperatures. The arithmetical mean surface roughness values of FePd films formed on MgO(001), (110), and (111) substrates after annealing at 600 °C are 0.2, 0.2, and 0.3 nm, respectively. The L1₀-FePd film formed on MgO(001) substrate shows a perpendicular magnetic anisotropy, whereas the L1₀-FePd films formed on MgO(110) and (111) substrates have in-plane anisotropies. The magnetic anisotropy is influenced by the c-axis distribution and the order degree.

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  Relation among structure of Ru underlayer and atomic layer stacking structure and uniaxial magnetocrystalline anisotropy (K_u) of sputtered Co films was discussed. Small torque with amplitude below theoretical limit |K_u^Cobulk-2π(M_s^Cobulk)²| = 6.8×10⁶ erg/cm³ was obtained for Co film with thickness d_Co ＜ 30 nm deposited on rough Ru underlayer. Structure analysis of the thin Co films with d_Co ＜ 30 nm deposited on rough Ru underlayer demonstrated that: 1) Magnitude of stacking faults were less than 1%, which meant the Co films had almost perfect hcp stacking, 2) Lattice constant c was expanded about 0.6% with retaining lattice constant a, 3) Thin Co films had rough surface which reflected morphology of the Ru underlayer. According to these results, it was thought that initial Co growth reflected vertical stacking of Ru underlayer on inclined crystal plane of the rough Ru underlayer. K_u was derived by correcting torque amplitude with self-demagnetizing energy considering surface morphology of Co film. K_u took maximal value of 5.0×10⁶ erg/cm³ at d_Co = 30 nm, and rapidly decreased with decreasing d_Co. Reduction of K_u in d_Co ＜ 30 nm might be caused by decrement of crystallographic uniaxial anisotropy for Co film due to expansion of the c axis.

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