Magnetic recording medium and method for its production

Claim 2

A magnetic recording medium having a magnetic thin film represented by the following formula CO 100-a-b-x-y-z Ni a Cr b Pt x M y O z wherein a, b, x, y and z are atomic % satisfying 0≦a≦15, 0 ≦b≦15, 0<x≦20, 0<y≦20, 0<z≦40, y+z≦40, and a+b+x+y+z≦60, a and b not simultaneously being 0, and M is at least one element selected from the group consisting of Si, B, Zr, Al, P, Ti, Sn and In.

Claim 3

The magnetic recording medium according to claim 1, wherein M in the formula of the magnetic thin film comprises an oxide in the form of MO c wherein 0<c≦5.

Claim 4

The magnetic recording medium according to claim 1, wherein the magnetic thin film has a squareness S and a coercive squareness S* in an in-plane magnetic hysteresis curve of at least 0.7.

Claim 5

A magnetic recording medium having a magnetic thin film represented by the following formula Co 100-a-b-x-y-z Ni a Cr b Pt x M y O z wherein a, b, x, y and z are atomic % satisfying 0≦a≦15, 0≦b≦15, 0 <x ≦20, 0<y ≦20, 0<z ≦40, y+z≦40, and a+b+x+y+z ≦60, a and b not simultaneously being 0, and M is at least one element selected from the group consisting of Si, B, Zr, Al, P, Ti, Sn and In, prepared by the method which comprises forming the magnetic thin film by a sputtering method using a target having an oxide MO d , wherein 0<d≦5, of at least one element selected from the group consisting of Si, B, Zr, Al, P, Ti, Sn and In incorporated into a base material of a CoNiPt alloy, a CoCrPt alloy or a CoNiCrPt alloy.

Claim 6

A magnetic recording medium having a magnetic thin film represented by the following formula Co 100-a-b-x-y-z Ni a Cr b Pt x M y O z wherein a, b, x, y and z are atomic % satisfying 0≦a≦15, 0≦b≦15, 0 <x ≦20, 0<y ≦20, 0<z ≦40, y+z≦40, and a+b+x+y+z ≦60, a and b not simultaneously being 0, and M is at least one element selected from the group consisting of Si, B, Zr, Al, P, Ti, Sn and In, prepared by the method which comprises forming the magnetic thin film by a sputtering method using a target having an oxide MO d , wherein 0<d≦5, of at least one element selected from the group consisting of Si, B, Zr, Al, P, Ti, Sn and In incorporated into a base material of a CoNiPt alloy, a CoCrPt alloy or a CoNiCrPt alloy.

Claim 7

The magnetic recording medium according to claim 4, prepared by a method wherein said oxide in the target is the same form of oxide as present in the magnetic film.