Hematite particles and magnetic recording medium using hematite particles as non-magnetic particles for a non-magnetic undercoat layer

摘要

Acicular hematite particles for use as non-magnetic particles for a non-magnetic undercoat layer of a magnetic recording medium contain 0.05 to 50 % by weight of aluminum, calculated as Al; have an average major axial diameter of not more than 0.3 mu m and a pH value of not less than 8; and contain not more than 300 ppm of soluble sodium salt, calculated as Na, and not more than 150 ppm of soluble sulfate, calculated as SO4.