US 11,798,588 B2
Magnetic recording medium
Masaru Terakawa, Miyagi (JP); Yoichi Kanemaki, Miyagi (JP); and Minoru Yamaga, Miyagi (JP)
Assigned to Sony Corporation, Tokyo (JP)
Appl. No. 16/609,135
Filed by Sony Corporation, Tokyo (JP)
PCT Filed Apr. 24, 2018, PCT No. PCT/JP2018/016649
§ 371(c)(1), (2) Date Oct. 28, 2019,
PCT Pub. No. WO2018/199105, PCT Pub. Date Nov. 1, 2018.
Claims priority of application No. 2017-090762 (JP), filed on Apr. 28, 2017.
Prior Publication US 2020/0098390 A1, Mar. 26, 2020
This patent is subject to a terminal disclaimer.
Int. Cl. G11B 5/667 (2006.01); G11B 5/73 (2006.01); G11B 5/706 (2006.01); G11B 5/712 (2006.01); G11B 5/65 (2006.01); H01F 1/147 (2006.01)
CPC G11B 5/667 (2013.01) [G11B 5/653 (2013.01); G11B 5/70642 (2013.01); G11B 5/712 (2013.01); G11B 5/73919 (2019.05); H01F 1/147 (2013.01)] 15 Claims
OG exemplary drawing
 
1. A magnetic recording medium having a recording track width of 2 μm or less, comprising:
a recording layer containing a powder of particles containing ε iron oxide, wherein
a squareness ratio measured in a transport direction is 30% or less,
a squareness ratio S1 measured in the transport direction and a squareness ratio S2 measured in a width direction satisfy a relationship S1≥S2,
a coercive force is 230 kA/m or greater and 300 kA/m or less at 25° C.,
an activation volume is 8000 nm3 or less, and
in a switching field distribution (SFD) curve, a peak ratio X/Y of a main peak height X and a height Y of a sub-peak near zero magnetic field is 3.0 or greater.