3D micromagnetism‐magnetostatic coupling technique for MR reading heads modeling

The purpose of this paper is to develop an original approach to simulate the reading process for multitrack shielded magneto‐resistive reading (MR) heads.

The shields and the media are of micron size while the sensor has sizes comparable with the characteristic length scales of the magnetic materials which are of the order of nanometer. Because of this large difference of scales between the different parts of the head, the macroscopic shields and the media are described by a boundary element method (BEM) approach, while the sensor is treated by micromagnetism in order to reconstruct the response of shielded multitrack MR head. To select the most favorable approach, several releases were implemented and compared. A technique based on a full‐coupling procedure was found to be the most general but too expensive in time. Appling the perfect‐imaging method directly into the micromagnetic simulator, the authors succeed in accelerating the computation without loosing accuracy.

Solving by BEM the Poisson equation for the scalar magnetic potential only the surfaces interfaces are discretised, saving thus computation time and memory resources. In addition, for multi‐tracks data pattern, the magnetic scalar potential may be estimated with a good approximation by considering a periodic system along the crosstrack direction. By applying the Fourier series expansion for the magnetic charges distribution along the crosstrack direction, the initial BEM 3D problem can be treated as a bi‐dimensional one.

This macroscopic‐microscopic coupling technique allows a full description of the behaviour of the magnetic sensor in its environment, being a useful tool for the design and the optimisation of the multitrack MR reading heads.