Micromagnetic studies of thin metallic films (invited)

Abstract

Anomalous metamagnetic-like transition in a FeRh/Fe3Pt interface occurring at T ≈ 120 K in the field-cooledcooling curves for low magnetic fields AIP Advances 2, 032168 (2012) Electric-field-control of magnetic anisotropy of Co0.6Fe0.2B0.2/oxide stacks using reduced voltage J. Appl. Phys. 112, 033919 (2012) Observation of intriguing exchange bias in BiFeO3 thin films J. Appl. Phys. 112, 033915 (2012) Rotary transportation of magnetic nanoparticle chains on magnetic thin film array A computer simulation model has been developed to conduct micromagnetic studies of thin magnetic films. Thin-film media are modeled as a planar hexagonal array of hexagonally shaped grains. Each grain is a single domain particle whose magnetization reverses by coherent rotation. The computation utilizes coupled gyromagnetic dynamic equations with phenomenological Landau-Lifshitz damping. In particular, the effects of particle interactions are investigated. The effect of media microstructure on magnetic hysteresis is examined a~ well as the effect of intergranular exchange coupling. The difference between planar and completely random orientation of the crystalline anisotropy axes is discussed. Recorded transitions are simulated by allowing a pair of perfect transitions to relax. With no intergranular exchange coupling, the transitions show profound irregularity and zig-zag structure. Intergranular exchange coupling produces more uniform transitions with increased zig-zag structure amplitude. For a closely spaced transition pair, the equilibrium configuration yields percolated transition boundaries with stable reverse island domains. The effect of gyromagnetic precession also has been examined.

ACTIVATION VOLUME OF FePt-TaN NANOCRYSTALLINE THIN FILMS WITH HIGH COERCIVITY

“…On the other hand, the values of normalised coercive force HclH k grain generally indicates the stren~th of intergranular exchange coupling [4,5]. The HeI Hkgram value of the present samples is almost a constant of 0.05-0.07.…”

“…The HeI Hkgram value of the present samples is almost a constant of 0.05-0.07. This suggests that the degree of intergranular magnetic coupling does not change remarkably against TA' It should be mentioned here that these values of HclH k gralO are a few times smaller than that of Co based thin film media (4], and several times smaller than the simulated value for the ideal media with no intergranular exchange coupling (HclHkgrain = about 0045) [2,5]. This result means that there is still a certain strength of intergranular exchange coupling.…”

Strong dependence of the Fe thin-film magnetic anisotropy on the Si(111) substrate preparation

“…As can be seen, there is rather good agreement between experimental and calculated data for this magnetically isotropic sample. The only noticeable discrepancy is that the squareness of the experimental loop is slightly higher than the model one, which has been assigned to intergranular interactions, 14 which were not taken into consideration in our calculations.…”

Anomalous X-ray Scattering for Determination of Nanostructured Alloy Formation and Site-specific Chemistry of Bragg Peak

“…The segregation to two crystalline phases with the same d-spacing is equivalent to a single phase inhomogencous alloy. Since Cr did not preferentially segregate to grain boundaries, a resultant higher magnetic exchange coupling [20] and reduced magnetocrystalline anisotropy constant [21] would reduce the coercivity. Since Pt is known to increase the local disorder and thus coercivity by increasing the magnetocrystalline anisotropy [22], the lower coercivity of 60 nm film [5] suggested that less Pt existed in the CoCrPt (002) Bragg peak, compared with that of 30 nm film.…”