IRON OXIDE POWDER FOR UNDERCOAT LAYER OF COAT-TYPE MAGNETIC RECORDING MEDIUM HAVING MULTILAYER STRUCTURE AND A PROCESS OF PRODUCING THE SAME

摘要

PROBLEM TO BE SOLVED: To provide an iron oxide powder for forming an underlayer of a coating type magnetic recording medium having a multilayered structure, having excellent dispersibility, capable of forming the underlayer having surface smoothness, high strength, low light transmittance and low specific resistance and capable of suppressing deterioration of a metal powder for magnetic recording in a magnetic layer.;SOLUTION: A cobalt containing iron oxide powder is provided, having 0.02 to 0.3 μm average major axis diameter, an axial ratio (major axis diameter/minor axis diameter) of 2 to 13, 40 to 100 m²/g BET specific surface area value, pH of 6 to 8, ≤50 ppm elution quantity of a soluble cation and ≤50 ppm elution quantity of a soluble anion and containing 0.2 to 10 at% cobalt compound to total iron expressed in terms of cobalt.;COPYRIGHT: (C)2004,JPO