Spin-Vortex構造の磁化反転

概要

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For a circular dot whose lateral size is larger than the exchange length l_<ex> (=^<1/2>/M_s), it is well known that the stable remanent state is a vortex structure where the spins around the center of the dot direct upward or downward. If only these two states are allowed in the vortex structure, it is possible to use it as a bi-stable memory element. To check this possibility, we investigated the vertical magnetization process of sub-micron permalloy dots through experiments and calculations. MFM detected distinct spin-vortex structures in which spins around dot centers were directed upward or downward and the switching field was strongly dependent on the dot shape. This result suggests the possibility of spin vortex structures as bi-stable switching memory elements, although their average remanence is quite small. LLG calculations show that lateral dimension of the spin vortex coincides with the exchange length l_<ex>=A^<1/2>/M_s〜15 nm regardless of the dot diameter.
社団法人日本磁気学会の論文
2002-04-01