Sumitomo Metal Mining Company, Ltd.

Hiroko Sekiya

Ryuichi Kuzuo

Kenji Ohmori

Atsushi Kawamoto

Junya Tada

Disclosed are magnetic discs having (A) a Cr-layer, as a lower layer, which has a composition comprising (1) substantially Cr or (2) 10% by weight or less of one or more selected from Cu, Nb, Ti, V, Zr, Mo, Zn, W and Ta, and a balance of being substantially Cr, and (B) a magnetic recording medium layer, as an upper layer, which has a composition comprising (1) substantially Co, (2) 30% by weight or less of Ni and a balance of being substantially Co, (3) 10% by weight or less of one or more selected from Y, La, Ce, Pr, Nd, Sm, Gd, Tb and Dy, and a balance of being substantially Co, (4) 30% by weight or less of Ni, 10% by weight or less of one or more selected from Y, La, Ce, Pr, Nd, Sm, Gd, Tb and Dy, and a balance of being substantially Co, (5) 10% by weight or less of one or more selected from Cu, Nb, Ti, V, Cr, Zr, Mo, Zn, W and Ta, and a balance of being substantially Co, (6) 30% by weight or less of Ni, 10% by weight or less of one or more selected from Cu, Nb, Ti, V, Cr, Zr, Mo, Zn, W and Ta, and a balance of being substantially Co, (7) 10% by weight or less of one or more selected from Y, La, Ce, Pr, Nd, Sm, Gd, Tb and Dy, 10% by weight or less of one or more selected from Cu, Nb, Ti, V, Cr, Zr, Mo, Zn, W and Ta, and a balance of being substantially Co, or (8) 30% by weight or less of Ni, 10% by weight or less of one or more selected from Y, La, Ce, Pr, Nd, Sm, Gd, Tb and Dy, 10% by weight or less of one or more selected from Cu, Nb, Ti, V, Cr, Zr, Mo, Zn, W and Ta, and a balance of being substantially Co, both as formed on a non-magnetic substrate, except those where the lower layer has the composition (1) and the upper layer has the composition (1) or (2) as well as those where the lower layer has the composition (1) and the upper layer has the composition (5) or (6) containing only one or more of Cr, Ta and/or W. The magnetic discs have noticeably improved magnetic characteristics and/or corrosion-resistance.

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Ichikawa, Japan

Hiroko Sekiya