US-20260128061-A1 - MAGNETIC RECORDING MEDIUM, METHOD OF MANUFACTURING MAGNETIC RECORDING MEDIUM, AND MAGNETIC STORAGE DEVICE

Abstract

A magnetic recording medium includes, in a following order, a substrate, an underlayer, a first magnetic layer, and a second magnetic layer, wherein the first magnetic layer includes a magnetic particle having an L1 0 structure, the second magnetic layer has a granular structure including a magnetic particle having an L1 0 structure, and a grain boundary including hexagonal boron nitride, a (111) plane of the magnetic particle included in the first magnetic layer is covered with an alloy of VN, Si 3 N 4 , YN, or TiN at an interface with the second magnetic layer, the magnetic particle in the second magnetic layer epitaxially grows from a (001) plane of the magnetic particle in the first magnetic layer, and the magnetic particle in the first magnetic layer and the magnetic particle in the second magnetic layer are columnar crystals that penetrate the first magnetic layer and the second magnetic layer, respectively.

Inventors

• Takayuki Fukushima
• Masaru Tajima

Assignees

• RESONAC HARD DISK CORPORATION

Dates

Publication Date

20260507

Application Date

20251027

Priority Date

20241101

Claims (4)

1. 1 . A magnetic recording medium comprising, in a following order: a substrate; an underlayer; a first magnetic layer; and a second magnetic layer, wherein: the first magnetic layer includes a magnetic particle having an L1 0 structure; the second magnetic layer has a granular structure including: a magnetic particle having an L1 0 structure; and a grain boundary including hexagonal boron nitride; a (111) plane of the magnetic particle included in the first magnetic layer is covered with an alloy of VN, Si 3 N 4 , YN, or TiN at an interface with the second magnetic layer; the magnetic particle included in the second magnetic layer epitaxially grows from a (001) plane of the magnetic particle included in the first magnetic layer; and the magnetic particle included in the first magnetic layer and the magnetic particle included in the second magnetic layer are columnar crystals that penetrate the first magnetic layer and the second magnetic layer, respectively.
2. 2 . The magnetic recording medium according to claim 1 , wherein the magnetic particle having the L1 0 structure included in the first magnetic layer and the magnetic particle having the L1 0 structure included in the second magnetic layer are FePt alloy particles.
3. 3 . A method of manufacturing a magnetic recording medium, the magnetic recording medium including, in a following order, a substrate, an underlayer, a first magnetic layer, and a second magnetic layer, wherein: the first magnetic layer includes a magnetic particle having an L1 0 structure; the second magnetic layer has a granular structure including: a magnetic particle having an L1 0 structure; and a grain boundary including hexagonal boron nitride; a (111) plane of the magnetic particle included in the first magnetic layer is covered with an alloy of VN, Si 3 N 4 , YN, or TiN at an interface with the second magnetic layer; the magnetic particle included in the second magnetic layer epitaxially grows from a (001) plane of the magnetic particle included in the first magnetic layer; and the magnetic particle included in the first magnetic layer and the magnetic particle included in the second magnetic layer are columnar crystals that penetrate the first magnetic layer and the second magnetic layer, respectively, the method comprising: forming the first magnetic layer by sputtering; forming the second magnetic layer by sputtering; and forming, by sputtering, an alloy layer of VN, Si 3 N 4 , YN, or TiN between the forming the first magnetic layer and the forming the second magnetic layer.
4. 4 . A magnetic storage device comprising a magnetic recording medium, the magnetic recording medium including, in a following order, a substrate, an underlayer, a first magnetic layer, and a second magnetic layer, wherein: the first magnetic layer includes a magnetic particle having an L1 0 structure; the magnetic layer has a granular structure including: a magnetic particle having an L1 0 structure; and a grain boundary including hexagonal boron nitride; a (111) plane of the magnetic particle included in the first magnetic layer is covered with an alloy of VN, Si 3 N 4 , YN, or TiN at an interface with the second magnetic layer; the magnetic particle included in the second magnetic layer epitaxially grows from a (001) plane of the magnetic particle included in the first magnetic layer; and the magnetic particle included in the first magnetic layer and the magnetic particle included in the second magnetic layer are columnar crystals that penetrate the first magnetic layer and the second magnetic layer, respectively.

Description

CROSS-REFERENCE TO RELATED APPLICATION The present application is based on and claims priority to Japanese patent application No. 2024-193165 filed on Nov. 1, 2024, with the Japan Patent Office, the entire contents of which are hereby incorporated by reference. BACKGROUND OF THE INVENTION 1. Field of the Invention The disclosures herein relate to magnetic recording media, methods of manufacturing magnetic recording media, and magnetic storage devices. 2. Description of the Related Art In recent years, a heat-assisted recording system or a microwave-assisted recording system, in which a magnetic recording medium is locally heated by irradiation with near-field light or microwaves to reduce coercive force, has attracted attention as a next-generation recording system capable of achieving a high areal density of approximately 2 Tbit/inch2. A magnetic head of such an assisted recording system enables easy recording on a magnetic recording medium having a coercive force of several tens of kOe at room temperature. As magnetic particles included in a magnetic layer of the magnetic recording medium, for example, magnetic particles having a high magnetocrystalline anisotropy constant (Ku) are used. Magnetic particles having a high magnetocrystalline anisotropy constant (Ku) can be reduced in size while maintaining thermal stability, which increase the coercive force at room temperature. As magnetic particles having a high magnetocrystalline anisotropy constant (Ku), for example, magnetic particles having an L10 structure such as Fe—Pt alloy particles (Ku: maximum 7×106 J/m3) and Co—Pt alloy particles (Ku: maximum 5×106 J/m3) are known. As a magnetic layer using magnetic particles having an L10 structure, for example, Non-Patent Literature 1 discloses a magnetic layer having a granular structure in which FePt magnetic particles having an L10 structure are covered with layers of hexagonal boron nitride. Here, it is desired to further improve areal density of a magnetic recording medium. In order to further improve the areal density of the magnetic recording medium, it is important to further reduce a particle size of the magnetic particles included in the magnetic layer and further increase anisotropy of the magnetic particles. As such a magnetic layer, a magnetic layer having a granular structure including FePt magnetic particles oriented in a (001) direction with an L10 structure and hexagonal boron nitride in grain boundaries (hereinafter, simply referred to as “FePt-hBN granular magnetic layer”) has been proposed. The hexagonal boron nitride has a layered structure in which (001) planes are stacked in parallel. Since hexagonal boron nitride tends to form grain boundaries between the FePt magnetic particles, particle size of the FePt magnetic particles can be reduced. In addition, since hexagonal boron nitride has low reactivity with the FePt magnetic particles, it does not hinder ordering of the magnetic particles. It is preferable to form hexagonal boron nitride such that the (001) plane surrounds the lateral surfaces of the FePt magnetic particles. However, in the related art, the magnetic particles and the grain boundaries tend to form a layered structure separated from each other, and the granular structure tends not to be formed in the FePt-hBN granular magnetic layer. In addition, components of the grain boundaries such as BN tend not to be sufficiently crystallized and tend to be in an amorphous state. Therefore, even if a magnetic layer (also referred to as a granular magnetic layer) having a granular structure is used, the areal density of the magnetic recording medium may not be improved. One aspect of the present disclosure aims to provide a magnetic recording medium in which the areal density is further improved by stably maintaining a state in which the granular magnetic layer forms a granular structure inside. CITATION LIST Non-Patent Literature [Non-Patent Literature 1] B. S. D. Ch. S. Varaprasad et al., “FePt—BN granular HAMR media with high grain aspect ratio and high L1 ordering on Corning Lotus™ NXT glass”, AIP Advances, Volume 13, Issue 3, 035002 (2023) SUMMARY OF THE INVENTION The above object can be achieved by the following. (1) A magnetic recording medium including, in a following order: a substrate;an underlayer;a first magnetic layer; anda second magnetic layer, wherein:the first magnetic layer includes a magnetic particle having an L10 structure;the second magnetic layer has a granular structure including: a magnetic particle having an L10 structure; anda grain boundary including hexagonal boron nitride; a (111) plane of the magnetic particle included in the first magnetic layer is covered with an alloy of VN, Si3N4, YN, or TiN at an interface with the second magnetic layer;the magnetic particle included in the second magnetic layer epitaxially grows from a (001) plane of the magnetic particle included in the first magnetic layer; andthe magnetic particle included in the