Magnetic thin film and method for forming the film, and magnetic thin film-applied device

#1. Field of the Invention

#The present invention relates to a magnetic thin film and a method for forming the film, and to a magnetic thin film-applied device, in particular to a magnetic thin film that comprises an alloy having an L11-type ordered structure and to a method for forming the film, and also to a device to which the film is applied. The magnetic thin film-applied device includes typically magnetic recording media such as perpendicular magnetic recording media, as well as tunnel magneto-resistance (TMR) devices, magnetoresistive random access memories (MRAM), microelectromechanical system (MEMS) devices; and in addition, the film is widely applicable to other known magnetic thin film-having devices and the like in accordance with their needs.

#2. Background Art

#FIG. 1 is a schematic cross-sectional view of a perpendicular magnetic recording medium of one embodiment of the invention.

#FIG. 2 is a schematic cross-sectional view of a perpendicular magnetic recording medium of another embodiment of the invention, differing from FIG. 1.

#FIG. 3 shows a schematic constitution of a magnetoresistive random access memory (MRAM) having a tunnel magneto-resistance (TMR) device of one embodiment of the invention.

#In the drawings, 1 is a non-magnetic substrate, 2 is a seed layer, 3 is an underlayer, 4 is a magnetic layer, and 5 is a protective layer.

#The outline and the advantages of the L11-type ordered structure and the magnetic thin film of an alloy having the structure, as well as the outline of the method of forming the magnetic thin film are described below, with reference to a Co—Ni—Pt alloy as one embodiment of the invention. The same shall apply also to another Co—Fe—Pt alloy of the invention from the viewpoint of the technical idea of the invention, though there may be some partial differences in point of the properties and the like therebetween.

#The L11-type structure is a crystal structure with a basis of an fcc structure, having a periodic regularity in point of the atomic position therein. Concretely, in the structure, the closest atomic plane, (111 plane) has a laminate structure of an atomic layer plane having a main ingredient of (Co—Ni) and an atomic layer plane having a main ingredient of Pt as alternately laminated one by one. For example, a completely-ordered L11-type structure of a (Co—Ni)50Pt50 composition, in which the constitutive atoms are ordered all at the individual ideal positions, is meant to indicate a structure where an atomic layer plane of Co—Ni alone and an atomic layer plane of Pt alone are alternately laminated one by one. In fact, it may be impossible to constitute such an ideal structure, but it is desirable to enlarge as much as possible the ratio S/Smax, that is, the degree of order as normalized by the maximum value Smax of a theoretically practicable degree of order, in consideration of the stoichiometric ratio of the existing atoms.