Design of CF-SPT head having large recording field and small stray field using 3-D ON/OFF method

The optimal design of a magnetic recording head is one important issue for high magnetic recording of 600-Gb/in(2) and beyond. In this paper, a three-dimensional topology optimization method (ON/OFF method) combined with a finite-element method is applied for the optimization of a cusp field single-pole-type head. In the ON/OFF method, the unknown variable is the reluctivity of magnetic material in the design domain and there is no special constraint. Therefore, the possibility of finding more optimal topology is increased compared with the conventional optimization method in which the design variables are specified. The optimal shape and dimension of a head is determined so that the flux density in a recording bit becomes the maximum and the leakage flux in the adjacent bit and adjacent track becomes the minimum. The recording field of 1.75 T and the field gradient of 0.038 T/nm (380 Oe/nm) are obtained for the head-soft underlayer distance of 25 nm.