Research Of Nanomagnetic Strcture Devices By Micromagnetic

This thesis investigated magnetisation dynamics in nanostructured ferromagneticmaterials by micromagnetic. The magnetisations with different time and directions wereobtained using the open solver OOMMF. The data was thoroughly analysed using myown softwawre. Resonance frequency, region and band structure were drawn. At last,band structure of antidot was calculated by PWM (Plan Wave Method).First, the dynamic susceptibility spectra of antidot array films with two sublatticeswere investigated. Due to the nonuniformity of the static magnetization patterns, twomain resonance peaks are found in our investigation when the diameter ratio of the twosublattices varies from5:5to5:3. The higher peak is around12GHz and can beidentified with the precession of magnetization between the next-nearest neighbor holes.The lower one, located around4GHz, is owing to the precession of magnetizationbetween the nearest neighbor holes. A new peak appears when diameter ratio is5:2,5:1and5:0.A novel planar structure of magnonic-crystal waveguide (MCW) with periodicrectangular-shaped holes embedded in a magnetic nanostrip film was designed. Theeffects of the distance between rectangular-shaped holes in the width direction of MCWon magnonic band structures were studied by micromagnetic simulations. The resultsshow that a MCW with a single magnonic band gap can be obtained by adjusting thedistance to meet the condition of Bragg reflection of spin waves in the width directionof MCW. Moreover, the center frequency and width of magnonic gap can be regulatedby changing the period and length of rectangular-shaped holes.At last，magnon band gaps (MBGs) in2D square and honeycomb lattices ofcircular cross-section rods can be increased by introducing a smaller diameter rod intothe center of each lattice unit cell. The additional lattice scatterers reduce the structuresymmetry to create significantly larger band gaps for original lattice. Magnon bandstructures are numerically calculated using the plane-wave method. The results showthat the normalized width of band gaps in square-hybrid-rods andhoneycomb-hybrid-rods structure are167%and285%sizes of those in the corresponding square-single-rods and honeycomb-single-rods structure. Crystalsymmetry reduction by introducing additional scatterers opens up a new way forengineering MBGs of2D magnonic crystals.