Effect of Coil Position on Magnetization Dynamics of Multilayered Hard Disk Writer Yokes

Three partially built hard disk writer structures with active coil windings located at different positions relative to the yoke were studied by time resolved scanning Kerr microscopy. All three Cartesian components of the magnetization were recorded simultaneously. Time resolved signals recorded near the pole tip showed that the component of magnetization parallel to the driving field had the same rise time irrespective of the location of the coil winding, but largest amplitude when the active coil was located near the middle of the yoke. Dynamic images obtained from three devices showed “flux beaming” in a channel parallel to the driving field. The magnetic contrast was strongest when the active coil was located near the centre of the yoke, while relaxation after removal of the excitation was most complete when the active coil was located near the confluence region. These results confirm the need for a multiturn coil to ensure effective flux propagation along the entire length of the yoke.