Initializing process on direct overwrite method using exchange-coupled quadilayer magneto-optical film
A direct overwrite mechanism of the exchange-coupled quadri-layered film using light intensity modulation has been investigation. The initializing process in the overwrite mechanism was studied. It was found that the writing layer had two different coercivities depending on the magnetization state of its adjacent layers. The coercivity of the writing layer in the initializing process was lower than that of the single layer. Thus, the overwrite recording was achieved with good recording characteristics. How this phenomenon plays a critical role in the initializing process was clarified. It was also found that this process occurred well above room temperature. >
Overwrite characteristics of magneto-optical disks by exchange-coupled RE-TM quadrilayered films
The direct overwrite characteristics by light power modulation on a magnetooptical disk with exchange coupled rare-earth-transition-metal (RE-TM) quadrilayers film are described. In this system, it is important to investigate the relationship between the laser power and the bias field margins. These margins are defined by the Curie temperature and the temperature dependence of the reversal field of each layer. Good recording characteristics were obtained, such as a carrier-to-noise ratio >49 dB on a bit length of 0.76 mu m. A fairly wide power margin of +or-20% was obtained, and a wide tolerance on the bias magnet construction was allowed. For achieving a read cycle of more than 10/sup 8/, it was necessary to keep the read power smaller than 1.5 mW at 2400 rpm. >
Static bubble domain properties of amorphous Gd–Co films
Metallic Gd1−xCox films (0.75 < × <0.85) obtained in the amorphous state by an rf‐sputtering were investigated using the Kerr polar magneto‐optic effect. These films exhibit perpendicular anisotropy sufficient to sustain magnetic cylindrical domains. The magnetic properties obtained with a Kerr hysteresigraph from these films can be described in terms of the wall energy model developed originally for nonmetallic single‐crystal bubble material. An analysis based on a simple molecular field description of the magnetization and a mean field approximation of the exchange constant A gives estimates of the uniaxial anisotropy energy Ku. The results indicate that for the composition range studied A increases linearly from 5.7 to 6.6 (10−7 erg/cm), while Ku ranges between 1 and 7 (105 erg/cm3). The saturation magnetization Ms varies between 30 and 180 G. The moderate anisotropy (Q=Ku/2πMs2 = 1–9) and low wall motion coercivity of less than 1 Oe are favorable to bubble device applications. The effect of thermal an...