Perpendicular magnetic recording medium, manufacturing method thereof, and magnetic storage device

A perpendicular magnetic recording medium, comprising:

• a substrate;
• a soft magnetic underlayer that is formed on the substrate;
• a seed layer made of a non-crystalline material, which seed layer is formed on the soft magnetic underlayer;
• a first underlayer made of Ru or an Ru alloy including Ru as a main component, which first underlayer is formed on the seed layer;
• and
• a recording layer that is formed on the first underlayer;
• wherein
• the first underlayer includes a polycrystalline film that is formed by a plurality of first crystal grains that are bonded to each other via a crystal boundary portion;
• the recording layer is formed by successively laminating first through nth magnetic layers in consecutive order from the seed layer side (n corresponding to an integer greater than or equal to 3);
• the first through nth magnetic layers include a plurality of magnetic grains having easy magnetization axes in a substantially perpendicular direction with respect to the substrate surface, and nonmagnetic non-soluble phases segregating the magnetic grains of the first through nth magnetic layers, respectively;
• and
• atomic concentrations Y1˜Yn of the respective non-soluble phases of the first through nth magnetic layers are arranged such that Y1>Y2> . . . >Yn.

A perpendicular magnetic recording medium, comprising:

• a substrate;
• a soft magnetic underlayer that is formed on the substrate;
• a seed layer made of a non-crystalline material, which seed layer is formed on the soft magnetic underlayer;
• a first underlayer made of Ru or an Ru alloy including Ru as a main component, which first underlayer is formed on the seed layer;
• a recording layer that is formed on the first underlayer;
• and
• a protective film that is formed on the recording layer;
• wherein
• the first underlayer includes a polycrystalline film that is formed by a plurality of first crystal grains that are bonded to each other via a crystal boundary portion;
• the recording layer includes a plurality of magnetic grains having easy magnetization axes in a substantially perpendicular direction with respect to the substrate surface, and a nonmagnetic non-soluble phase segregating the magnetic grains;
• and
• an atomic concentration of the non-soluble phase in the recording layer is arranged to gradually decrease in a direction from an interface with the seed layer towards an interface with the protective layer.

A perpendicular magnetic recording medium, comprising:

• a substrate;
• a soft magnetic underlayer that is formed on the substrate;
• a seed layer made of a non-crystalline material, which seed layer is formed on the soft magnetic underlayer;
• a first underlayer made of Ru or an Ru alloy including Ru as a main component, which first underlayer is formed on the seed layer;
• and
• a recording layer including a first magnetic layer and a second magnetic layer that is laminated on the first magnetic layer, which recording layer is formed on the first underlayer;
• wherein
• the first underlayer includes a polycrystalline film that is formed by a plurality of first crystal grains that are bonded to each other via a crystal boundary portion;
• the first magnetic layer includes a plurality of first magnetic grains having easy magnetization axes in a substantially perpendicular direction with respect to the substrate surface, and a nonmagnetic non-soluble phase segregating the first magnetic grains from each other, which first magnetic layer is arranged to have a first saturation flux density;
• the second magnetic layer is made of a metallic hard magnetic material and includes a plurality of second magnetic grains having easy magnetization axes in a substantially perpendicular direction with respect to the substrate surface, which second magnetic layer is arranged to have a second saturation flux density;
• the second saturation flux density of the second magnetic layer is arranged to be higher than the first saturation flux density of the first magnetic layer;
• and
• the second magnetic grains of the second magnetic layer are arranged on surfaces of the first magnetic grains of the first magnetic layer.

A perpendicular magnetic recording medium, comprising:

• a substrate;
• a soft magnetic underlayer that is formed on the substrate;
• a seed layer made of a non-crystalline material, which seed layer is formed on the soft magnetic underlayer;
• a first underlayer made of Ru or an Ru alloy including Ru as a main component, which first underlayer is formed on the seed layer;
• and
• a recording layer that is formed on the first underlayer;
• wherein
• the first underlayer includes a polycrystalline film that is formed by a plurality of first crystal grains that are bonded to each other via a crystal boundary portion;
• the recording layer is formed by successively laminating first through nth magnetic layers and a metallic magnetic layer in consecutive order from the seed layer side (n corresponding to an integer greater than or equal to 3)
• the first through nth magnetic layers include a plurality of magnetic grains having easy magnetization axes in a substantially perpendicular direction with respect to the substrate surface, and nonmagnetic non-soluble phases segregating the magnetic grains of the first through nth magnetic layers, respectively;
• atomic concentrations Y1˜Yn of the respective non-soluble phases of the first through nth magnetic layers are arranged such that Y1>Y2> . . . >Yn;
• a saturation flux density of the metallic magnetic layer is arranged to be higher than saturation flux densities of the first through nth magnetic layers;
• and
• the metallic magnetic layer includes a plurality of metallic magnetic grains that are arranged on surfaces of the magnetic grains of the nth magnetic layer.

A perpendicular magnetic recording medium, comprising:

• a substrate;
• a soft magnetic underlayer that is formed on the substrate;
• a seed layer made of a non-crystalline material, which seed layer is formed on the soft magnetic underlayer;
• a first underlayer made of Ru or an Ru alloy including Ru as a main component, which first underlayer is formed on the seed layer;
• a recording layer that is formed on the first underlayer;
• and
• a protective film that is formed on the recording layer;
• wherein
• the first underlayer includes a polycrystalline film that is formed by a plurality of first crystal grains that are bonded to each other via a crystal boundary portion;
• the recording layer includes a composition modulated layer and a metallic magnetic layer, the composition modulated layer including a plurality of magnetic grains having easy magnetization axes in a substantially perpendicular direction with respect to the substrate surface and a nonmagnetic non-soluble phase segregating the magnetic grains;
• an atomic concentration of the non-soluble phase in the composition modulated layer is arranged to gradually decrease in a direction from an interface with the seed layer towards an interface with the metallic magnetic layer;
• a saturation flux density of the metallic magnetic layer is arranged to be higher than a saturation flux density of the composition modulated layer;
• and
• the metallic magnetic layer includes a plurality of metallic magnetic grains that are arranged on surfaces of the magnetic grains of the composition modulated layer at the interface with the metallic magnetic layer.

A magnetic storage device, comprising:

• a recording/reproducing unit including a magnetic head;
• and
• a perpendicular magnetic recording medium including
• a substrate;
• a soft magnetic underlayer that is formed on the substrate;
• a seed layer made of a non-crystalline material, which seed layer is formed on the soft magnetic underlayer;
• a first underlayer made of Ru or an Ru alloy including Ru as a main component, which first underlayer is formed on the seed layer;
• and
• a recording layer including a first magnetic layer and a second magnetic layer that is laminated on the first magnetic layer, which recording layer is formed on the first underlayer;
• wherein
• the first underlayer includes a polycrystalline film that is formed by a plurality of first crystal grains that are bonded to each other via a crystal boundary portion;
• the first magnetic layer includes a plurality of first magnetic grains having easy magnetization axes in a substantially perpendicular direction with respect to the substrate surface, and a first nonmagnetic non-soluble phase segregating the first magnetic grains from each other, which first non-soluble phase is provided at a first atomic concentration;
• the second magnetic layer includes a plurality of second magnetic grains having easy magnetization axes in a substantially perpendicular direction with respect to the substrate surface, and a second nonmagnetic non-soluble phase segregating the second magnetic grains from each other, which second non-soluble phase is provided at a second atomic concentration;
• and
• the first atomic concentration of the first non-soluble phase in the first magnetic layer is arranged to be higher than the second atomic concentration of the second non-soluble phase in the second magnetic phase.

A magnetic storage device, comprising:

• a recording/reproducing unit including a magnetic head;
• and
• a perpendicular magnetic recording medium including
• a substrate;
• a soft magnetic underlayer that is formed on the substrate;
• a seed layer made of a non-crystalline material, which seed layer is formed on the soft magnetic underlayer;
• a first underlayer made of Ru or an Ru alloy including Ru as a main component, which first underlayer is formed on the seed layer;
• and
• a recording layer that is formed on the first underlayer;
• wherein
• the first underlayer includes a polycrystalline film that is formed by a plurality of first crystal grains that are bonded to each other via a crystal boundary portion;
• the recording layer is formed by successively laminating first through nth magnetic layers in consecutive order from the seed layer side (n corresponding to an integer greater than or equal to 3);
• the first through nth magnetic layers include a plurality of magnetic grains having easy magnetization axes in a substantially perpendicular direction with respect to the substrate surface, and nonmagnetic non-soluble phases segregating the magnetic grains of the first through nth magnetic layers, respectively;
• and
• atomic concentrations Y1˜Yn of the respective non-soluble phases of the first through nth magnetic layers are arranged such that Y1>Y2> . . . >Yn.

A magnetic storage device, comprising:

• a recording/reproducing unit including a magnetic head;
• and
• a perpendicular magnetic recording medium including
• a substrate;
• a soft magnetic underlayer that is formed on the substrate;
• a seed layer made of a non-crystalline material, which seed layer is formed on the soft magnetic underlayer;
• a first underlayer made of Ru or an Ru alloy including Ru as a main component, which first underlayer is formed on the seed layer;
• a recording layer that is formed on the first underlayer;
• and
• a protective film that is formed on the recording layer;
• wherein
• the first underlayer includes a polycrystalline film that is formed by a plurality of first crystal grains that are bonded to each other via a crystal boundary portion;
• the recording layer includes a plurality of magnetic grains having easy magnetization axes in a substantially perpendicular direction with respect to the substrate surface, and a nonmagnetic non-soluble phase segregating the magnetic grains;
• and
• an atomic concentration of the non-soluble phase in the recording layer is arranged to gradually decrease in a direction from an interface with the seed layer towards an interface with the protective layer.

A magnetic storage device, comprising:

• a recording/reproducing unit including a magnetic head;
• and
• a perpendicular magnetic recording medium including
• a substrate;
• a soft magnetic underlayer that is formed on the substrate;
• a seed layer made of a non-crystalline material, which seed layer is formed on the soft magnetic underlayer;
• a first underlayer made of Ru or an Ru alloy including Ru as a main component, which first underlayer is formed on the seed layer;
• and
• a recording layer including a first magnetic layer and a second magnetic layer that is laminated on the first magnetic layer, which recording layer is formed on the first underlayer;
• wherein
• the first underlayer includes a polycrystalline film that is formed by a plurality of first crystal grains that are bonded to each other via a crystal boundary portion;
• the first magnetic layer includes a plurality of first magnetic grains having easy magnetization axes in a substantially perpendicular direction with respect to the substrate surface, and a nonmagnetic non-soluble phase segregating the first magnetic grains from each other, which first magnetic layer is arranged to have a first saturation flux density;
• the second magnetic layer is made of a metallic hard magnetic material and includes a plurality of second magnetic grains having easy magnetization axes in a substantially perpendicular direction with respect to the substrate surface, which second magnetic layer is arranged to have a second saturation flux density;
• the second saturation flux density of the second magnetic layer is arranged to be higher than the first saturation flux density of the first magnetic layer;
• and
• the second magnetic grains of the second magnetic layer are arranged on surfaces of the first magnetic grains of the first magnetic layer.

A magnetic storage device, comprising:

• a recording/reproducing unit including a magnetic head;
• and
• a perpendicular magnetic recording medium including
• a substrate;
• a soft magnetic underlayer that is formed on the substrate;
• a seed layer made of a non-crystalline material, which seed layer is formed on the soft magnetic underlayer;
• a first underlayer made of Ru or an Ru alloy including Ru as a main component, which first underlayer is formed on the seed layer;
• and
• a recording layer that is formed on the first underlayer;
• wherein
• the first underlayer includes a polycrystalline film that is formed by a plurality of first crystal grains that are bonded to each other via a crystal boundary portion;
• the recording layer is formed by successively laminating first through nth magnetic layers and a metallic magnetic layer in consecutive order from the seed layer side (n corresponding to an integer greater than or equal to 3);
• the first through nth magnetic layers include a plurality of magnetic grains having easy magnetization axes in a substantially perpendicular direction with respect to the substrate surface, and nonmagnetic non-soluble phases segregating the magnetic grains of the first through nth magnetic layers, respectively;
• atomic concentrations Y1˜Yn of the respective non-soluble phases of the first through nth magnetic layers are arranged such that Y1>Y2> . . . >Yn;
• a saturation flux density of the metallic magnetic layer is arranged to be higher than saturation flux densities of the first through nth magnetic layers;
• and
• the metallic magnetic layer includes a plurality of metallic magnetic grains that are arranged on surfaces of the magnetic grains of the nth magnetic layer.

A magnetic storage device, comprising:

• a recording/reproducing unit including a magnetic head;
• and
• a perpendicular magnetic recording medium including
• a substrate;
• a soft magnetic underlayer that is formed on the substrate;
• a seed layer made of a non-crystalline material, which seed layer is formed on the soft magnetic underlayer;
• a first underlayer made of Ru or an Ru alloy including Ru as a main component, which first underlayer is formed on the seed layer;
• a recording layer that is formed on the first underlayer;
• and
• a protective film that is formed on the recording layer;
• wherein
• the first underlayer includes a polycrystalline film that is formed by a plurality of first crystal grains that are bonded to each other via a crystal boundary portion;
• the recording layer includes a composition modulated layer and a metallic magnetic layer, the composition modulated layer including a plurality of magnetic grains having easy magnetization axes in a substantially perpendicular direction with respect to the substrate surface and a nonmagnetic non-soluble phase segregating the magnetic grains;
• an atomic concentration of the non-soluble phase in the composition modulated layer is arranged to gradually decrease in a direction from an interface with the seed layer towards an interface with the metallic magnetic layer;
• a saturation flux density of the metallic magnetic layer is arranged to be higher than a saturation flux density of the composition modulated layer;
• and
• the metallic magnetic layer includes a plurality of metallic magnetic grains that are arranged on surfaces of the magnetic grains of the composition modulated layer at the interface with the metallic magnetic layer.

A method of manufacturing a perpendicular magnetic recording medium that includes a substrate on which a soft magnetic underlayer, a seed layer, a first underlayer, a first magnetic layer, and a second magnetic layer are consecutively formed, which first and second magnetic layers respectively include a plurality of magnetic grains having easy magnetization axes in a direction substantially perpendicular to the substrate surface and nonmagnetic non-soluble phases segregating the magnetic grains, the method comprising the steps of:

• forming the seed layer made of a non-crystalline material on the soft magnetic underlayer;
• forming the first underlayer made of Ru or an Ru alloy including Ru as main component on the seed layer;
• forming the first magnetic layer on the first underlayer through sputtering using a first sputtering target;
• and
• forming the second magnetic layer on the first magnetic layer through sputtering using a second sputtering target;
• wherein
• the first sputtering target and the second sputtering target include a hard magnetic material and a nonmagnetic material that is made of any one of an oxide, a carbide, or a nitride;
• and
• the first sputtering target includes the nonmagnetic material at an atomic concentration that is higher than an atomic concentration of the nonmagnetic material in the second sputtering target.

A method of manufacturing a perpendicular magnetic recording medium that includes a substrate on which a soft magnetic underlayer, a seed layer, a first underlayer, a first magnetic layer, and a second magnetic layer are consecutively formed, which first and second magnetic layers respectively include a plurality of magnetic grains having easy magnetization axes in a direction substantially perpendicular to the substrate surface and nonmagnetic non-soluble phases segregating the magnetic grains, the method comprising the steps of:

• forming the seed layer made of a non-crystalline material on the soft magnetic underlayer;
• forming the first underlayer made of Ru or an Ru alloy including Ru as main component on the seed layer;
• forming the first magnetic layer on the first underlayer through sputtering using a first sputtering target including a hard magnetic material and a nonmagnetic material that is made of any one of an oxide, a carbide, or a nitride;
• and
• forming the second magnetic layer on the first magnetic layer through sputtering using a second sputtering target that is made of a hard magnetic material.