Perpendicular magnetic recording medium and manufacturing of the same
View Patent ↗Embodiments of the embodiment are directed to reducing the inter-granular exchange coupling of an oxide granular medium and obtaining a high media S/N value, resulting in an areal recording density greater than 23 gigabits per square centimeter or more being achieved. In one embodiment, a magnetic recording medium comprises a structure laminating a soft-magnetic underlayer, a lower intermediate layer including Ru, an upper intermediate layer consisting of Ru crystal grains and oxide crystal grain boundaries, a magnetic recording layer consisting of crystal grains and oxide crystal grain boundaries, in order, on a substrate, growing crystal grains of the magnetic recording layer epitaxially on the Ru crystal grains of the upper intermediate layer, and growing the crystal grain boundaries of the magnetic recording layer on the crystal grain boundaries of the upper intermediate layer.
1. A perpendicular magnetic recording medium, comprising:
a substrate;
a soft-magnetic underlayer deposited on said substrate;
a lower intermediate layer containing Ru deposited on said soft-magnetic underlayer;
an upper intermediate layer deposited on said lower intermediate layer and having Ru crystal grains and oxide crystal grain boundaries;
a magnetic recording layer deposited on said upper intermediate layer and having crystal grains and oxide crystal grain boundaries,
wherein the crystal grains of said magnetic recording layer grow epitaxially on the Ru crystal grains of said upper intermediate layer, and the crystal grain boundaries of said magnetic recording layer grow on the crystal grain boundaries of said upper intermediate layer,
wherein said magnetic recording layer consists of a CoCrPt-based alloy to which is added at least one selected from the group consisting of Si oxide, Al oxide, Ti oxide, Cr oxide and Mg oxide, and
wherein a difference in position in the depth direction, at which the contents of oxygen and Co maintain 95% of the value of respective contents thereof at the mid position in the depth direction of said magnetic recording layer, is 1 nm or less in a depth profile of the element content around the interface of said magnetic recording layer with said upper intermediate layer obtained by making discharge of an oxide target faster than that of a magnetic target during formation of said magnetic layer.
2. A perpendicular magnetic recording medium according to 1 , wherein said lower intermediate layer includes Ru or a Ru-based alloy.
3. A perpendicular magnetic recording medium according to 1 , wherein the crystal grain boundaries of said upper intermediate layer comprise at least one material selected from the group consisting of Si oxide, Al oxide, Ti oxide, Cr oxide, and Mg oxide.
4. A perpendicular magnetic recording medium according to 1 , wherein the content of the main element, except for oxygen, constituting the grain boundaries of said upper intermediate layer obtained by a composition analysis using X-ray photoelectron spectroscopy (XPS) is the same as or less than the content of the main element, except for oxygen, constituting the grain boundaries of said magnetic recording layer.
5. A perpendicular magnetic recording medium according to 1 , wherein the thickness of said upper intermediate layer is 1 nm or more and 6 nm or less.
6. A perpendicular magnetic recording medium according to 1 , wherein the main element, except for oxygen, constituting the grain boundaries of said upper intermediate layer is identical to the main element, except for oxygen, constituting the grain boundaries of said magnetic recording layer.