Shigemi Mizukami

Ferromagnetic resonance (FMR) was measured for Cu/permalloy (Py) (20, 30, 40 \AA{})/Cu ${(d}_{\mathrm{Cu}})/\mathrm{Pt}$ (0, 50 \AA{}) films with various ${d}_{\mathrm{Cu}}$ to clarify the effect of spin diffusion driven by the precession of magnetization on Gilbert damping. The peak-to-peak linewidth $\ensuremath{\Delta}{H}_{\mathrm{pp}}$ of the FMR spectra for Cu/Py/Cu/Pt films was very large at ${d}_{\mathrm{Cu}}=0\mathrm{\AA{}},$ and decreased remarkably at ${d}_{\mathrm{Cu}}=30\mathrm{\AA{}

The out-of-plane angular dependence of ferromagnetic resonance (FMR) was measured for NM/80NiFe(Py)/NM (NM=Cu, Ta, Pd and Pt) films with various Py, Cu and Ta thicknesses fabricated by magnetron sputtering. The out-of-plane angular dependences of FMR resonance field and linewidth were analyzed using Landau-Lifshitz-Gilbert equation taking account of broadening of linewidth due to magnetic inhomogeneities in a film. Magnetic inhomogeneities were assumed to be the fluctuation of magnitude and dire

Spin precession with frequencies up to 280 GHz is observed in Mn(3-δ)Ga alloy films with a perpendicular magnetic anisotropy constant K(u)∼15 M erg/cm(3). The damping constant α, characterizing macroscopic spin relaxation and being a key factor in spin-transfer-torque systems, is not larger than 0.008 (0.015) for the δ=1.46 (0.88) film. Those are about one-tenth of α values for known materials with large K(u). First-principles calculations well describe both low α and large K(u) for these alloys

Gilbert damping for the epitaxial Co2FeAl Heusler alloy films was investigated. Gilbert damping constant for the films was evaluated by analyzing the data of ferromagnetic resonance measured at the frequency of 2–20 GHz. Gilbert damping constant for the film without annealing was rather large, while it decreased remarkably with postannealing. Gilbert damping constant for the film annealed at 600 °C was ≃0.001. These behavior of Gilbert damping constant can be well explained by the fact that the

To investigate the correlation between perpendicular magnetic anisotropy and intrinsic Gilbert damping, time-resolved magneto-optical Kerr effect was measured in Pt/Co(dCo)/Pt films. These films showed perpendicular magnetization at dCo=1.0 nm and a perpendicular magnetic anisotropy energy Kueff that was inversely proportional to dCo. With an analysis based on the Landau–Lifshitz–Gilbert equation, the intrinsic Gilbert damping constant α was evaluated by parameter-fitting of frequency and lifeti

Mn-Ga binary alloys show strong magnetism and large uniaxial magnetic anisotropy even though these alloys do not contain any noble, rare-earth metals or magnetic elements. We investigate the composition dependence of saturation magnetization ${M}_{\mathrm{S}}$ and uniaxial magnetic anisotropy ${K}_{\mathrm{u}}$ in epitaxial films of Mn${}_{x}$Ga${}_{1\ensuremath{-}x}$ alloys ($x\ensuremath{\sim}0.5$--0.75) grown by magnetron sputtering. The ${M}_{\mathrm{S}}$ values decrease linearly from approx

Fast magnetization precession is observed in L10-FePt alloy epitaxial thin films excited and detected by all-optical means. The precession frequency varies from 45 to 65 GHz depending on the applied magnetic field strength and direction, which can be explained by a uniform precession model taking account of first- and second-order uniaxial magnetic anisotropy. The lowest effective Gilbert damping constant has a minimum value of 0.055, which is about half that in Co/Pt multilayers and is comparab

Gilbert damping is reported in perpendicularly magnetized Ni/Co multilayer films with Pt buffer and capping layers, and investigated through the time-resolved magneto-optical Kerr effect under various applied magnetic field strengths and directions. Both damping constant α and perpendicular magnetic anisotropy energy Ku depend strongly on layer thickness and bilayer periodicity, and rise to approximately 0.08 and 8 Merg/cm3, respectively. The Gilbert damping rate depends linearly on inverse mult

First-principles calculation of D022 Mn3Ge shows a fully spin-polarized Δ1 band at the Fermi level, low saturation magnetization MS=180 emu/cm3, high uniaxial magnetic anisotropy Ku=23 Merg/cm3, and low Gilbert damping α=9×10-4. We also experimentally investigate D022 Mn3+xGe epitaxial films grown on MgO(100) substrates with different compositions x. The films exhibit a coercivity of about 20 kOe, MS of about 130 emu/cm3, and Ku of about 10 Merg/cm3 at x=0.55 (78 at.% Mn). These indicate that D0

We have investigated magnetic field strength (up to 10 kOe) and angle dependences of spin dynamics in 4-nm-thick films of CoCrPt alloys with perpendicular magnetic anisotropy using the all-optical time-resolved magneto-optical Kerr effect (TRMOKE). The comprehensive TRMOKE measurements have indicated the Gilbert damping constant α of 0.05 for the alloy film with low coercivity. The experiments also indicated that α values for the alloy films deposited at higher temperatures with higher coercivit

Epitaxial growth and magnetization precessional dynamics for tetragonal MnAlGe films are investigated. The films are grown on MgO (100) with c axis parallel to the film normal and well-ordered layered structures. The film exhibits rectangular hysteresis loop with perpendicular magnetic anisotropy constant of 4.7 Merg/cm3 and saturation magnetization of 250 emu/cm3. Magnetization precession with precession frequency of ∼100 GHz is observed by time-resolved magneto-optical Kerr effect. Further, th