AVS 46th International Symposium
    Magnetic Interfaces and Nanostructures Technical Group Monday Sessions
       Session MI+VM+AS-MoA

Invited Paper MI+VM+AS-MoA3
Micromagnetic Properties and Recording Performance in High Density Magnetic Recording Media

Monday, October 25, 1999, 2:40 pm, Room 618/619

Session: Magnetic Recording: Media and Heads
Presenter: T. Suzuki, Toyota Technological Institute, Japan
Authors: T. Suzuki, Toyota Technological Institute, Japan
G. Lauhoff, Toyota Technological Institute, Japan
Correspondent: Click to Email
In order to increase areal recording density, much effort has been made to improve magnetic charactreristics and microstructure in magnetic recording media. In order for decreasing noise and for realizing a sharp transition between written bits, an inter-granular exchange coupling must be lowered, which enhances a thermal instability of magnetization. Given this conditions, it is vitally important to understand the role of magnetic activation volume or magnetic coupled region in conjunction with micromagnetics, which plays a key role in noise mechanisms. The present study is to discuss activation volume in longitudinal magnetic recording media of various types including CoCrPtTa thin-films and granular-type recording media. The activation volume is evaluated based on the time decay of magnetization at a certain field. A novel method to define the activation volume is proposed. The Barkhausen volume is estimated through the field-sweep-rate dependence of coercivity. It is found that the activation volume, which is of the order of 10@super -18@ cm@super -3@, decreases with applied field, then levels off, and starts increases at fields beyond coercivity. This trend is found for all the high density recording media of CoCrPtTa and granular-type media under consideration. The recording noise is found to be closely related to activation volume. Measurments of @delta@M curves suggest that lesser the granular-exchange-coupling is, the smaller the activation volume becomes.