Magnetic recording medium comprising a magnetic layer having specific thickness, surface roughness and projections

1. A magnetic recording medium comprising a non-magnetic support, at least one primer layer formed on one surface of the non-magnetic support, a magnetic layer formed on the primer layer, and a backcoat layer formed on the other surface of the non-magnetic support, wherein the backcoat layer has a thickness of 0.2 to 0.8 μm, the magnetic layer has a thickness of 0.30 μm or less and a centerline average surface roughness Ra of 3.2 μm or less, and (P 1 −P 0 ) is 30 nm or less and (P 1 −P 20 ) is 5 nm or less in which P 0 is an averaged height of projections of the magnetic layer, and P 1 , P 2 , - - - and P 20 are heights of the highest, the second highest, - - - and the 20th highest projections of the magnetic layer, respectively, when they are measured in a field of view of 350 μm×260 μm on the magnetic layer.

2. The magnetic recording medium according to claim 1 , wherein (P 1 −P 0 ) is from 5 nm to 30 nm.

3. The magnetic recording medium according to claim 1 , which is recorded and read with a reading head comprising a magnetoresistance effect element.

4. The magnetic recording medium according to claim 1 , wherein said magnetic layer has a coercive force of 120 to 320 kA/m, and a product of a residual magnetic flux density in the machine direction of said magnetic layer and a thickness of said magnetic layer is from 0.0018 Tμm to 0.06 Tμm.

5. The magnetic recording medium according to claim 1 , wherein said non-magnetic support has a Young's modulus in a machine direction of at least 6.08 GPa (at least 600 kg/mm 2 ), and a ratio of a Young's modulus MD in the machine direction to a Young's modulus TD in a transverse direction (MD/TD) is from 0.6 to 1.8.