1. Department of Electrical Engineering, Faculty of Engineering, Khon Kaen University, Khon Kaen, Thailand
2. Asia Engineering Department, Seagate Technology, Nakhon Ratchasima, Thailand
3. Recording Head Group, Seagate Technology, Bloomington, Minnesota 55345, USA
4. Seagate Research Group, Seagate Technology, Shakopee, Minnesota 55379, USA
5. Seagate Technology, Derry BT48 0BF, United Kingdom