HDDs are common information storage devices. With improvements in recording density of magnetic HDDs, there has been a demand for improving the performance of magnetic heads and magnetic recording media. In a magnetic hard disk drive, a magnetic head is embedded in a slider that flies above the surface of a magnetic recording medium.
Recently, a technology so-called thermal assisted magnetic recording (TAMR) has been proposed, and a thermal assisted magnetic head also has been put to use. The technology uses a magnetic recording medium having high coercivity. When writing data, a write magnetic field and heat are applied almost simultaneously to the area of the magnetic recording medium where to write data, so that the area rises in temperature and drops in coercivity for data writing. The area where data is written subsequently falls in temperature and rises in coercivity to increase the thermal stability of magnetization.
Commonly, the heat source comes from the thermal assisted magnetic head. FIG. 1a shows a perspective view of a conventional thermal assisted magnetic head 100. The thermal assisted magnetic head 100 includes a slider body 110 having an air bearing surface (ABS) (not shown, under) processed so as to provide an appropriate flying height and a light source unit 130 mounted on the slider body 110. The slider body 110 includes a bottom surface 112 opposite the ABS, a trailing edge 113 where read and write elements 115 are embedded, and a leading edge (not shown, back) opposite the trailing edge 113. The light source unit 130 is mounted on the position where the write elements are embedded via a bonding layer. The light source unit 130 includes a light source 131 located near the write element and a substrate member 132 for supporting the light source 131. The substrate member 132 is bonded to the slider body 110 by using a solder layer, for example. The light source 131 has a laser diode embedded therein which emits a laser light to a portion of the magnetic recording medium, which reduces the medium's coercivity. After that, writing is performed by applying write magnetic field to the heated portion; therefore the writing operation is facilitated.
As shown in FIG. 1b, since the power of the laser light periodic, thus the power is unstable. When the laser diode is turned off, the temperature is decreased gradually, after a certain time, the laser diode is turned on to make the temperature rise again. By this token, the temperature of the laser diode is unstable, thus the writing operation on the disk track is unstable.
Thus, it is desired to provide an improved light source unit and a thermally-assisted magnetic head to overcome the above-mentioned drawbacks.