High Frequency Properties Of Nanoscale Magnetic Materials In Micromagnetic Simulation

With the develop of perpendicular recording media, high ferquency in Wireless transmission technology, high density of store information, the decrease of electronic device sizes, people pay more and more attention in the high frequency magnetic materials at nanoscale. In this article, ultrafast magnetization switch and the microwave dynamic response near steady state have been studied via OOMMF (micromagnetic simulation), The main results are as follows:1Ultrafast magnetization switch in simulations have been studied by changing an ultra-short pulse waveform of magnetic field, size and direction in FePt (FeCo) particle system (5nm x5nm x5nm). We found that the ultrashort magnetic field pulses can drive the magnetization, so it realized the Magnetizations switching in picosecond and stabilized in the direction of magnetic reversal; Compared to the original direction of magnetization, the critical field is0.385times as large as the uniaxial anisotropy field HA when the ultrashort magnetic field pulses at125°With the increase of damping coefficient(0-0.8), the critical curves are more and more close to the S-W astroid. Our work is valuable for the magnetic reversal theory and the development of rapid information magnetic storage.2Around a ladder of nano-structure material (five steps in maximum), the magnetic spectrums have been studied by changing the structure and thickness of each layer in simulations and the physical nature have also been discussed. The results found that:Single-layer films only have two peaks in their corresponding magnetic spectrums, two resonant peaks associated with a bulk and an edge mode in the imaginary part of magnetic conductivity; in multi-layer ladder structures, we found multi-peaks in the magnetic spectrums, the multi-peaks are much more significant with the increase of thickness, and its anisotropic equivalent field increase gradually; when the imaginary part of magnetic conductivity have multi-peaks, Bulk and edge modes can not explain the magnetic spectrum anymore. For this, we use the response of the external field, and find out the parts of the magnetization corresponding different frequency.