Dynamics of laminated write elements

Abstract

One concern as storage technology moves to perpendicular recording is the remnant state of the writer top pole. In principal, a remnant state with a substantial magnetization density perpendicular to the recording medium can lead to the unwanted erasure of data. Also, it is desirable to have the writer reach a nonerasing remnant state as quickly as possible. One technique to reduce the magnetization in the remnant state is to laminate the pole tip with some nonmagnetic material [Y. Satoh, A. Ohtsubo, and Y. Shimada, IEEE Trans. Magn. 21, 1551 (1985); S. Wang et al., IEEE Trans. Magn. 30, 3897 (1994)]. We have performed fully micromagnetic simulations of write elements with eight, five, four, and two laminates coupled antiferromagnetically. Results are presented for recording fields, as well as for the decay of the magnetization to a remnant state. The two- and four-laminate write elements typically have a vortex induced in the pole tip, and this vortex tends to survive, even in the remnant state. This can give rise both to a slow decay as well as large remnant fields from the out-of-plane magnetization in the vortex. On the other hand, the magnetization of the eight-laminate pole tip decays by “scissoring” of the magnetization in the laminates, with a faster decay to the remnant state. However, locally large divergences of the magnetization density can give rise to “hot spots” with relatively large remnant fields.