MAGNETIC RECORDING MEDIUM

1 . A magnetic recording medium comprising:

a substrate;

a seed layer;

an under layer; and

a perpendicular recording layer having a granular structure,

wherein (Ms·α·δ 1.5 (1−Rs) 0.33 ), Ms, and α satisfy the following relations:

(Ms·α·δ 1.5 (1−Rs) 0.33 )≦0.1 [μ·emu·(mm) −1.5 ],

Ms≧ 450 [emu/cc], and

α≧1.2, and

wherein in the above formulas, Ms indicates a saturated magnetization amount, α indicates the gradient of a M-H loop around a coercive force Hc, δ indicates the thickness of the perpendicular recording layer, and Rs indicates a squareness ratio.

2 . The magnetic recording medium according to claim 1 ,

wherein the seed layer has an amorphous state and includes a metal having a melting point of 2,000° C. or less.

3 . The magnetic recording medium according to claim 1 ,

wherein the seed layer has an amorphous state and includes an alloy containing Ti and Cr.

4 . The magnetic recording medium according to claim 1 ,

wherein (Ku·V/k B ·T) satisfies the following relation:

( Ku·V/k B ·T )≧65, and

wherein in the above formula, Ku indicates magnetic anisotropy energy, V indicates an activation volume, k B indicates Boltzmann constant, and T indicates the absolute temperature.

5 . The magnetic recording medium according to claim 1 ,

wherein the under layer includes Ru.

6 . The magnetic recording medium according to claim 1 ,

wherein the perpendicular recording layer has a granular structure in which grains containing Co, Pt, and Cr are separated from each other with oxides provided therebetween.

7 . The magnetic recording medium according to claim 6 ,

wherein the perpendicular recording layer has an average composition represented by the following formula (1):

(Co x Pt y Cr 100-x-y ) 100-z —(SiO 2 ) z   (1), and

wherein in the formula (1), x, y, and z satisfy 69≦x≦72, 12≦y≦16, 9≦z≦12, respectively.

8 . The magnetic recording medium according to claim 1 ,

wherein the substrate is a flexible non-magnetic substrate.