Patent ID: 7128989

Claim:
A magnetic recording medium comprising at least one magnetic layer comprising a ferromagnetic powder and a binder on a nonmagnetic support, wherein said ferromagnetic powder is a ferromagnetic hexagonal ferrite powder having an average plate diameter of 5 to 40 nm, and said binder comprises 0.25 to 0.65 meq/g of at least one polar group selected from —SO 3 M, —OSO 3 M, —PO(OM) 2 , —OPO(OM) 2 and —COOM (where M denotes a hydrogen atom, alkali metal or ammonium salt), and/or 0.5 to 5 meq/g of at least one polar group selected from —CONR 1 R 2 , —NR 1 R 2 and —NR 1 R 2 R 3 + (where R 1 , R 2 and R 3 independently denote hydrogen atoms or alkyl groups).