Magnetization Dynamics in CoFeB Buffered Perpendicularly Magnetized Co/Pd Multilayer (original) (raw)
Related papers
Perpendicular magnetic anisotropy and magnetization process in CoFeB/Pd multilayer films
Perpendicular magnetic anisotropy (PMA) and dynamic magnetization reversal process in [CoFeB t nm/Pd 1.0 nm] n (t = 0.4, 0.6, 0.8, 1.0, and 1.2 nm; n = 2 -20) multilayer films have been studied by means of magnetic hysteresis and Kerr effect measurements. Strong and controllable PMA with an effective uniaxial anisotropy up to 7.7×10 6 J.m -3 and a saturation magnetization as low as 200 emu/cc are achieved. Surface/interfacial anisotropy of CoFeB/Pd interfaces, the main contribution to the PMA, is separated from the effective uniaxial anisotropy of the films, and appears to increase with the number of the CoFeB/Pd bilayers. Observation of the magnetic domains during a magnetization reversal process using polar magneto-optical Kerr microscopy shows the detailed behavior of nucleation and displacement of the domain walls.
Damping of Magnetization Precession in Perpendicularly Magnetized CoFeB Alloy Thin Films
Applied Physics Express, 2012
Gilbert damping is investigated in perpendicularly magnetized CoFeB thin films using ferromagnetic resonance and time-resolved magneto-optical Kerr effect. The CoFeB films were deposited on a MgO layer and annealed at different temperatures. The lowest effective damping constant eff values were 0.017, 0.013, and 0.009 for the films annealed at 250, 300, and 350 C, respectively; these values were smaller than the values reported previously. #
Dynamical behaviour of ultrathin [CoFeB (tCoFeB)/Pd] films with perpendicular magnetic anisotropy
Scientific Reports
CoFeB-based ultrathin films with perpendicular magnetic anisotropy are promising for different emerging technological applications such as nonvolatile memories with low power consumption and high-speed performance. In this work, the dynamical properties of [CoFeB (tCoFeB)/Pd (10 Å)]5 multilayered ultrathin films (1 Å ≤ tCoFeB ≤ 5 Å) are studied by using two complementary methods: time-resolved magneto-optical Kerr effect and broadband ferromagnetic resonance. The perpendicular magnetization is confirmed for multilayers with tCoFeB ≤ 4 Å. The effective perpendicular magnetic anisotropy reaches a clear maximum at tCoFeB = 3 Å. Further increase of CoFeB layer thickness reduces the perpendicular magnetic anisotropy and the magnetization became in-plane oriented for tCoFeB ≥ 5 Å. This behaviour is explained by considering competing contributions from surface and magnetoelastic anisotropies. It was also found that the effective damping parameter αeff decreases with CoFeB layer thickness a...
Thickness dependent magnetization dynamics of perpendicular anisotropy Co/Pd multilayer films
Journal of Magnetism and Magnetic Materials, 2011
We present the measurements of the picosecond magnetization dynamics of Co/Pd multilayer films. The dynamic magnetization properties of sputtered multilayer films were analyzed as a function of Co layer thicknesses and applied bias field. Both the eigenfrequencies of the magnetization precession in the multilayers and the associated Gilbert damping exhibit extreme sensitivity to the magnetic layer thickness on an atomic monolayer scale. The eigenfrequency increases more than threefold when the Co thickness decreases from 7.5 to 2.8Å, mainly due to the changes in effective saturation magnetization and perpendicular anisotropy constant. A concomitant 2.6-fold increase in the damping of the oscillations is observed and attributed to stronger interface dissipation in thinner Co layers. In addition, we introduce a quasi-1D micromagnetic model in which the multilayer stack is described as a onedimensional chain of macrospins that represent each Co layer. This model yields excellent agreement with the observed resonance frequencies without any free parameters, while being much simpler and faster than full 3D micromagnetic modeling.
Physical Review B, 2014
The magnetization dynamics of both Ta/CoFeB/MgO and Ta/CoFeB/Ta films were investigated using an all-optical pump-probe method. The magnetic field strength and the applied field direction dependencies of the precession frequency and the relaxation time were explained well by the Landau-Lifshitz-Gilbert equation when taking the magnetic anisotropy distribution in the film into account. The thickness dependence of the α values obtained for both stacked films was also discussed. The α values increased linearly with increasing inverse CoFeB thickness (t CoFeB ). The slope of the α vs 1/t CoFeB characteristic for Ta/CoFeB/MgO films was smaller than that for Ta/CoFeB/Ta films, implying that the enhancement of α was caused by the CoFeB/Ta interface. Comparison of the annealing temperature dependence of α and the perpendicular magnetic anisotropy constant K u revealed no correlation between α and K u .
Thickness dependent magneto-static and magneto-dynamic properties of CoFeB thin films
Journal of Vacuum Science & Technology A
The authors report thickness dependent magneto-static and magneto-dynamic properties of amorphous Co 40 Fe 40 B 20 films with thickness, t = 10-200 nm deposited on thermally oxidized Si substrates using magnetron sputtering technique at ambient temperature. Magnetic hysteresis loops of films with t ≤ 20 nm transformed from rectangular or flat type shape to transcritical nature for t ≥ 50 nm. This is attributed to a change in the magnetic domain structure from in-plane magnetization with uniaxial anisotropy in thinner films to stripe domains with effective magnetic anisotropy in thicker films. Magnetization dynamics in the films has been investigated using ferromagnetic resonance spectra. Out-of-plane angular dependent resonance field (H r) and linewidth (ΔH) data have been interpreted using the Smit-Beljers formula. It is found that ΔH contains large extrinsic contribution with the major one being two-magnon scattering. An inverse scaling of Gilbert damping constant (α) with the film thickness over the entire thickness range of 10-200 nm is observed with the lowest α value of 0.004. The results reveal a cost effective strategy for developing films for spintronics based microwave devices and spin-transfer-torque based magnetic devices.
Magnetization Dynamics and Damping for L10-FePd Thin Films with Perpendicular Magnetic Anisotropy
Journal of the Magnetics Society of Japan, 2015
Magnetization dynamics and damping for FePd films were investigated using the all-optical time-resolved magneto-optical Kerr effect. We deposited 16-nm-thick FePd thin films on a single crystal MgO(001) substrate. Both in-plane magnetic anisotropy and perpendicular magnetic anisotropy (PMA) FePd films were fabricated using the magnetron sputtering method at various substrate temperatures T s . The dependencies of magnetization dynamics on the external magnetic field angle at fixed external magnetic field strengths were analyzed. The effective damping constant, α eff , for FePd films with PMA exhibited anisotropy, whereas the α eff for FePd with in-plane magnetic anisotropy did not depend significantly on the field angle. A uniaxial crystalline magnetic anisotropy constant, K u1 , of 11 Merg/cm 3 and a minimum for α eff of 0.007 were observed for film prepared at T s = 200 • C. This α eff value was much smaller than that for other Fe-and Co-based materials with large PMA such as L1 0 -FePt alloy, Co/Pt(Pd) multilayers.
Perpendicular Magnetic Anisotropy in CoFeB/Pd Bilayers
Magnetics, IEEE …, 2010
Perpendicular magnetic anisotropy is observed in ultrathin (~ 0.6 nm) amorphous Co40Fe40B20 when sputtered on an MgO (001) buffer layer and capped with Pd. The layers are superparamagnetic with a blocking temperature of ~ 230 K, below which they show an exponential temperature dependence of coercivity. Perpendicular magnetic anisotropy is observed in the as-deposited state and the mechanism is different from that of CoFeB/Pt, which requires postannealing. These ultrathin layers could be a model system for studies of electric field effects on magnetic anisotropy.
Applied Physics Letters, 2013
The relationship between Gilbert damping and magneto-crystalline anisotropy is studied here using an all-optical method in a perpendicular Co/Ni multilayer system by varying the Ti-buffer thickness. As the Ti-buffer thickness increases, the magneto-crystalline anisotropy is enhanced. The time-resolved Kerr signal of each sample is well described by its own intrinsic Gilbert damping constant in a wide range of the external magnetic field. Interestingly, we find that Gilbert damping constants increase linearly from 0.021 to 0.036 when the magneto-crystalline anisotropy of the samples varies from 2.4 to 3.4 Merg/cm 3 . Such a linear relationship implies that the spin-orbit interaction is the main source of the damping process through spin-lattice relaxation in our system. V C 2013 AIP Publishing LLC.