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Critical current density for spin transfer torque switching with composite free layer structure
유천열 한국물리학회 2010 Current Applied Physics Vol.10 No.3
Critical current density of composite free layer (CFL) in magnetic tunneling junction is investigated. CFL consists of two exchange coupled ferromagnetic layers, where the coupling is parallel or anti-parallel. Instability condition of the CFL under the spin transfer torque, which is related with critical current density,is obtained by analytic spin wave excitation model and confirmed by macro-spin Landau–Lifshitz–Gilbert equation. The critical current densities for the coupled two identical layers are investigated with various coupling strengths, and spin transfer torque efficiencies.
유천열,김남희 한국물리학회 2015 Current Applied Physics Vol.15 No.3
We investigate the condition for the skyrmion state formation in ultrathin ferromagnetic layers with the Dzyaloshinskii-Moriya interaction (DMI). By using micromagnetic simulations with DMI term, we found skyrmion state is a ground state instead of a collinear single domain when DMI is larger than a critical value. When the skyrmion arrays are formed, a specific length scale of skyrmion is governed the spin configurations. We found that the critical DMI energy density for the skyrmion state is related with not only crystalline anisotropy energy, but also the dipole-dipole interaction.
유천열(Chun-Yeol You) 한국자기학회 2005 韓國磁氣學會誌 Vol.15 No.4
Formation of a narrow magnetic domain wall is demonstrated by micromagnetics simulations. It is found that the domain wall width can be shrunk in a local exchange coupled system. The local exchange coupled system means that only a part of a ferromagnetic layer has an exchange coupling with another ferromagnetic layer. The system can be considered as two parts in the lateral dimensions: one is an exchange coupled region and another is a free region. Since the two regions have quite different local switching fields, the domain wall will be formed at the interface between the two regions at moderate field ranges.