US 11,721,360 B2
Magnetic recording medium
Takashi Kataguchi, Tokyo (JP); Natsuki Ichise, Tokyo (JP); and Takeshi Takahashi, Tokyo (JP)
Assigned to Sony Corporation, Tokyo (JP)
Filed by Sony Corporation, Tokyo (JP)
Filed on Nov. 17, 2021, as Appl. No. 17/528,900.
Application 17/528,900 is a continuation of application No. 17/257,461, granted, now 11,183,213, previously published as PCT/JP2020/025767, filed on Jul. 1, 2020.
Claims priority of application No. 2020-006553 (JP), filed on Jan. 20, 2020.
Prior Publication US 2022/0076699 A1, Mar. 10, 2022
This patent is subject to a terminal disclaimer.
Int. Cl. G11B 5/008 (2006.01); G11B 5/706 (2006.01); G11B 5/714 (2006.01); G11B 5/735 (2006.01); G11B 5/584 (2006.01); G11B 5/588 (2006.01); G11B 15/43 (2006.01)
CPC G11B 5/70678 (2013.01) [G11B 5/00817 (2013.01); G11B 5/714 (2013.01); G11B 5/735 (2013.01); G11B 5/584 (2013.01); G11B 5/588 (2013.01); G11B 15/43 (2013.01)] 20 Claims
OG exemplary drawing
 
1. A magnetic recording medium, comprising:
a base;
an underlayer that is provided over the base and includes a non-magnetic powder; and
a magnetic layer that is provided over the underlayer and includes a magnetic powder and a binder, wherein
an average particle volume V of the magnetic powder is 1600 nm3 or less,
an average thickness of the magnetic recording medium is 5.3 μm or less,
a thermal stability KuVact/kBT of the magnetic recording medium is 63 or more, and
a ratio Hrp/Hc1 of a residual coercive force Hrp of the magnetic recording medium measured using a pulsed magnetic field in a perpendicular direction to a coercive force Hc1 of the magnetic recording medium in the perpendicular direction is 1.98 or less.