MAGNETIC RECORDING MEDIUM

• US 20100227201A1
• Filed: 03/02/2010
• Published: 09/09/2010
• Est. Priority Date: 03/03/2009
• Status: Abandoned Application

• Current Assignee: Hitachi Maxell Limited (Maxell, Ltd.)
• Original Assignee: Hitachi Maxell Limited (Maxell, Ltd.)
• Inventors: Watanabe, Toshiyuki, SASAKI, Yuji, Inoue, Tetsutaro, Owaki, Takayuki
• Application Number:
  US12/715,990
• Publication Number:
  US 20100227201A1
• Time in Patent Office: Days
• US Class Current: 428/839
• CPC Class Codes: G11B 5/70 on a base layer
• CPC Class Codes: G11B 5/733 characterised by the addition of non-magnetic particles base layers having a non-magnetic layer under a soft magnetic layer G11B5/736; magnetic recording media substrates G11B5/739
• CPC Class Codes: G11B 5/7334 Base layer characterised by composition or structure

Abstract

A magnetic recording medium having a nonmagnetic substrate, and a soft magnetic layer and a ferromagnetic layer having a thickness of 5 to 150 nm formed in this order on the nonmagnetic substrate, in which, the ferromagnetic layer contains a spherical, ellipsoidal or plate-form ferromagnetic powder and a binder, and has an axis of easy magnetization substantially in a perpendicular direction, and the soft magnetic layer contains a spherical or ellipsoidal magnetite soft magnetic powder having a particle size of 30 nm or less, a rate of variation in particle size of 20% or less and a saturation magnetization of 10 to 60 Am²/kg, and a binder.

Claims

1. A magnetic recording medium comprising a nonmagnetic substrate, and a soft magnetic layer and a ferromagnetic layer having a thickness of 5 to 150 nm formed in this order on the nonmagnetic substrate, wherein

the ferromagnetic layer contains a spherical, ellipsoidal or plate-form ferromagnetic powder and a binder, and has an axis of easy magnetization substantially in a perpendicular direction, and

the soft magnetic layer contains a spherical or ellipsoidal magnetite soft magnetic powder having a particle size of 30 nm or less, a rate of variation in particle size of 20% or less and a saturation magnetization of 10 to 60 Am²/kg, and a binder.

2. The magnetic recording medium according to claim 1, wherein said magnetite soft magnetic powder has a coercive force of 2 to 12 kA/m.

3. The magnetic recording medium according to claim 1, wherein said ferromagnetic powder is a magnetic powder selected from the group consisting of an iron nitride-based magnetic powder and a Co-based ferromagnetic powder.

4. The magnetic recording medium according to claim 2, wherein said ferromagnetic powder is a magnetic powder selected from the group consisting of an iron nitride-based magnetic powder and a Co-based ferromagnetic powder.