US 6,280,813 B1 · Magnetic recording media with antiferromagnetically coupled ferromagnetic films as the recording layer

Abstract

A magnetic recording medium for data storage uses a magnetic recording layer having at least two ferromagnetic films antiferromagnetically coupled together across a nonferromagnetic spacer film. The magnetic moments of the two antiferromagnetically-coupled films are oriented antiparallel, and thus the net remanent magnetization-thickness product (Mrt) of the recording layer is the difference in the Mrt values of the two ferromagnetic films. This reduction in Mrt is accomplished without a reduction in the thermal stability of the recording medium because the volumes of the grains in the antiferromagnetically-coupled films add constructively. In a magnetic recording rigid disk application, the magnetic layer comprises two ferromagnetic films, each a granular film of a sputter deposited CoPtCrB alloy, separated by a Ru spacer film having a thickness to maximize the antiferromagnetic exchange coupling between the two CoPtCrB films. One of the ferromagnetic films is made thicker than the other, but the thicknesses are chosen so that the net moment in zero applied magnetic field is low, but nonzero.

Claims18

Dependent claims

A magnetic recording medium comprising:

a substrate;
a magnetic recording layer on the substrate and comprising a first ferromagnetic film having a magnetic moment per unit area, a nonferromagnetic spacer film on the first ferromagnetic film, and a second ferromagnetic film having a magnetic moment per unit area different from the moment per unit area of the first ferromagnetic film and being formed on the spacer film, the second ferromagnetic film being exchange coupled antiferromagnetically to the first ferromagnetic film across the spacer film, the magnetic recording layer exhibiting a major hysteresis loop with two remanent magnetic states in the absence of an applied magnetic field;
and
wherein the orientations of the moments of the first and second ferromagnetic films are substantially antiparallel in each remanent state, but the first ferromagnetic film's moment orientation in one remanent state is substantially antiparallel to its orientation in the other remanent state.

1 more element

A magnetic recording disk comprising:

a substrate;
an underlayer on the substrate;
a magnetic recording layer on the underlayer and comprising a first cobalt alloy ferromagnetic film having magnetic moment per unit area and comprising multiple magnetic domains with the orientations of the moments of the domains being generally randomly oriented, a nonferromagnetic spacer film of a material selected from the group consisting of ruthenium (Ru), chromium (Cr), rhodium (Rh), iridium (Ir), copper (Cu), and their alloys formed on and in contact with the first ferromagnetic film, and a second cobalt alloy ferromagnetic film having magnetic moment per unit area different then the magnetic moment per unit area of the first ferromagnetic film and comprising multiple magnetic domains formed on and in contact with the spacer film, the spacer film having a thickness sufficient to induce domains of the second ferromagnetic film to be exchange coupled antiferromagnetically to associated domains of the first ferromagnetic film across the spacer film with the orientations of the moments of the domains in the second ferromagnetic film being substantially antiparallel to the orientations of the moments of their associated domains in the first ferromagnetic film;
and
a protective overcoat formed on the magnetic recording layer.

2 more elements

Dependencies are inferred from the claim text.

Magnetic recording media with antiferromagnetically coupled ferromagnetic films as the recording layer

Life of this patent

Magnetic recording media with antiferromagnetically coupled ferromagnetic films as the recording layer

Life of this patent

Abstract

Claims18