1. Field of the Invention
The present invention relates to magnetic recording systems for writing information signals on a magnetic medium and, in particular, to a magnetic recording system employing a combination of magnetic write field gradient and thermal gradient to increase the areal density of magnetic recording, and to a ‘thermal spring’ magnetic recording media for recording information with such systems.
2. Description of the Related Art
Moving magnetic storage devices, especially magnetic disk drives, are the memory device of choice. This is due to their expanded non-volatile memory storage capability together with a relatively low cost. Thin film magnetic read/write heads are used for reading and writing magnetically coded data stored on a magnetic storage medium such as a magnetic disk.
Magnetic disk drives are information storage devices which utilize at least one rotatable magnetic media disk having concentric data tracks defined for storing data, a read/write transducer for reading data from and/or writing data to the various data tracks, a slider for supporting the transducer adjacent the data tracks typically in a flying mode above the storage media, a suspension assembly for resiliently supporting the slider and the transducer over the data tracks, and a positioning actuator coupled to the transducer/slider/suspension combination for moving the transducer across the media to the desired data track and maintaining the transducer over the data track center line during a read or a write operation. The transducer is attached to or is formed integrally with the slider which supports the slider above the data surface of the storage disk by a cushion of air, referred to as an air bearing, generated by the rotating disk.
There is a continuing strongly-felt need for increasing the data storage density in the magnetic media of the storage disks. Most efforts to increase magnetic storage density involve techniques for increasing the areal bit density in the magnetic storage medium. In rotating magnetic disk drives, the areal density is the product of the number of flux reversals, or bits, per unit length along a data track and the number of tracks available per unit length of disk radius. In current high areal density storage systems the bit density is in the range of 300-500×103 bits/inch and the track density is in the range of 20-36×103 tracks/inch resulting in an areal density of about 10-18 Gbits/in2. Advances to areal densities of 40-100 Gbits/in2 are probably achievable with the prior art technology by implementing careful control of media microstructure in order to ensure thermal stability of the stored data and to keep media noise within acceptable limits.
However, there is a problem with the prior art magnetic recording systems and the magnetic media as areal density is further increased to densities greater than about 100 Gbits/in2. As the track density increases, it becomes increasingly difficult to maintain the transducer centered over the very narrow data track during read and write operations. As the bit density along the track increases, a more fundamental problem arises due to the small size of the bits causing instability of the bit magnetization due to thermal fluctuations. As the bit size decreases, the energy of thermal fluctuations becomes comparable to the stored magnetic energy which is given by the product of the switching volume and the magneto-crystalline anisotropy of the material. This results in a decay of the bit magnetization and loss of the stored data.
Therefore, there is a need for a magnetic recording system that provides increased areal density of data with improved thermal stability and for a method of writing data on high areal density magnetic media in such a magnetic recording system.