Micromagnetic Investigation Of Magnetization Reversal In Polycrystalline Co Nanomagnets

Along with the rapid development of modern information economy, the requirement for memory capacity of digital information with write and read is increasingly enhanced, and people request faster response speed of it. Magnetic storage media and the magnetic read/write head is the important information storage means. Lattice medium technology has the most potential for the next generation recording technology application after the vertical recording schema. in the abstract, the storage density on Lattice medium technology can achieve twice as much as that of the traditional vertical recording technology. The basic element of lattice medium is single nanomagnet. In addition, MRAM is highly considered to have a prospect for dynamic memory. the triple layer nanomagnet with magnetoresistance effect is the memory elements of MRAM. Therefore, the research of nanomagnet magnetization reversal process not only enable us to understand the magnetization reversal mechanisms profound, but also provide useful guidance about how to improve the performance of magnetic storage. As a consequence, in this paper Co polycrystalline nanomagnets are studied. The investigation of polycrystalline Co nanomagnet magnetization reversal process is carried through by micromagnetic calculation with micromagnetic finite difference method.Micromagnetic finite difference method is used successively to simulate the demagnetization processes of polycrystalline Co circular and diamond-shaped nanomagnets. The circular disks have different diameter and thickness, yet the diamond-shaped magnets have different thickness. Analysising the nucleation, propagation, and annihilation process of the vortexs for the purpose of reducing the demagnetization energy, which results indicate that the shape anisotropy of nanomagnetic has a great influence on magnetization reversal process. Diamond-shaped nanomagnet with the thickness of 30 nm has high remanence and coercive force. magnetization reversal process of circular and diamond-shaped nanomagnet with artificial defect in the central of samples are calculated simultaneity. It is found that defects play a pinning effect on the vortexs. While the coercivity and remanence of diamond-shaped nanomagnet containing defects that thickness is 30 nm are _iH_c=-92.67 mT. J_x/J_S=0.892, respectively.Calculation and research a basic MRAM magnetic element -- pseudo-spin valve magnetization reversal process. thickness of spacer layer is about 20 nm, At the time, only the static magnetic coupling is considered , which exchange coupling can be omitted. The results show that the hysteresis loops of circular magnetic that diameter and thickness of two ferromagnetic are 400 nm, 10nm,60nm, respective, emerges a new dumbbell-side lobe structure; As to diamond-shaped pseudo-spin valve with a defect in its center, which long axis and minor axis are 400 nm and 380 nm, and the thickness of two ferromagnetic are 10 nm, 30nm separate, could gain a large coercivity, the coercivity corresponding is i H c=-98.6 mT and the remanence is J_x/J_S=0.442.