Patent Application
20080057350
The accompanying drawings, which are included to provide further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention. In the drawings:
In the following detailed description, numerous specific details are set forth to provide a full understanding of the present invention. It will be apparent, however, to one ordinarily skilled in the art that the present invention may be practiced without some of these specific details. In other instances, well-known structures and techniques have not been shown in detail to avoid unnecessarily obscuring the present invention.
The presence of the oxide compound acts to refine the grain size of magnetic data storage layer 106. This occurs as a result of the oxide compound being disposed in oxide-rich grain boundary phases 110, which act to separate the magnetic grains 109 of the high-Ku material, thereby contributing to the effective exchange decoupling of magnetic domains and an improved signal-to-noise ratio (“SNR”).
According to one aspect, the oxide compound is a compound of oxygen and a single element with a negative reduction potential. According to another aspect, the oxide compound is a compound of oxygen and multiple elements, at least one of which has a negative reduction potential. Table 1, below, illustrates a number of metals and metalloids with negative reduction potentials that are suitable for use as an oxide in a magnetic data storage layer of the present invention.
The thermal stability ratio for the magnetic domains of magnetic data storage layer 106 is given by Equation 1:
KuV/kBT (1)
where Ku is the anisotropy constant of the material of the magnetic domain, V is the size of the magnetic domain, kB is the Boltzmann constant, and T is the temperature of the magnetic domain in degrees Kelvin. As can be seen with reference to Equation 1, as the size V of a magnetic domain decreases, the anisotropy constant Ku must be increased to maintain the same thermal stability ratio. Accordingly, the high-Ku material permits the magnetic domains of magnetic data storage layer 106 to maintain an acceptable thermal stability ratio of about 50 to 70 as the size of the magnetic domains is reduced.
According to one aspect, the high-Ku material has an anisotropy constant of at least 0.5×107 ergs/cm3. For example, the high-Ku material may be chosen from materials such as L10-type ordered intermetallics, ordered HCP intermetallics, and rare earth transition metal alloys. Table 2, below, illustrates a number of materials with high anisotropy constants that are suitable for use as a first material in a magnetic data storage layer of the present invention.
While magnetic recording media stack 100 has been described with reference to a particular arrangement of layers, it will be apparent to one of skill in the art that the scope of the present invention is not limited to such an arrangement. Rather, the present invention has application to magnetic recording media which include more or less layers than magnetic recording media stack 100, and which are disposed in any arrangement known to those of skill in the art.
Turning to
According to another embodiment of the present invention, in which sputter target 200 is used to reactively sputter, in the presence of oxygen, a film such as magnetic data storage layer 106, sputter target 200 does not include an oxide compound. Rather, in addition to a high-Ku material (e.g., one of the alloys listed in Table 2), sputter target 200 includes a second material made up of one or more elements, at least one of which has a negative reduction potential (e.g., one or more of the elements listed in Table 1). This second material will combine with oxygen during the reactive sputtering process to provide the oxide compound for refining the grain size of a magnetic data storage layer reactively sputtered therefrom. According to one aspect, these two materials are combined in sputter target 200 as a single alloy. According to alternate aspects, these two materials may be provided as separate regions of sputter target 200, or combined in any one of a number of other ways readily apparent to those of skill in the art.
According to another aspect of the present invention, in which sputter target 200 is reactively sputtered in the presence of oxygen, sputtering chamber 302 is partially filled with both an inert gas and oxygen. Sputter target 200 is exposed to an electric field to excite both gas species to generate plasma. Some of the negative reduction potential elements which have been ejected off of sputter target 200 chemically react with oxygen in the plasma to form oxide compounds, which are deposited in film 300 on the surface of substrate 301.
While the present invention has been particularly described with reference to the various figures and embodiments, it should be understood that these are for illustration purposes only and should not be taken as limiting the scope of the invention. There may be many other ways to implement the invention. Many changes and modifications may be made to the invention, by one having ordinary skill in the art, without departing from the spirit and scope of the invention.
