The present invention provides: an aluminum alloy substrate for magnetic discs with excellent plating surface smoothness; a manufacturing method therefor; and a magnetic disc using said aluminum alloy substrate for magnetic discs. The present invention is an aluminum alloy substrate for magnetic discs, a manufacturing method therefor, and a magnetic disc using said aluminum alloy substrate for magnetic discs, the aluminum alloy substrate being characterized in being obtained from an aluminum alloy containing Mg: 2.0-8.0 mass % (% below), Be: 0.00001-0.00200%, Cu: 0.003-0.150%, Zn: 0.05-0.60%, Cr: 0.010-0.300%, Si: 0.060% or less, Fe: 0.060% or less, the balance being obtained from Al and unavoidable impurities.

A tape-shaped magnetic recording medium includes a substrate; and a magnetic layer that is provided on the substrate and contains a magnetic powder. An average thickness of the magnetic layer is not more than 90 nm, an average aspect ratio of the magnetic powder is not less than 1.0 and not more than 3.0, the coercive force Hc1 in a vertical direction is not more than 3000 Oe, the coercive force Hc1 in the vertical direction and a coercive force Hc2 in a longitudinal direction satisfy a relationship of Hc2/Hc10.8, and a value of 1.50.5 is not more than 0.6 N in a tensile test of the magnetic recording medium in the longitudinal direction, where 0.5 is a load at an elongation rate of 0.5% in the magnetic recording medium and 1.5 is a load at an elongation rate of 1.5% in the magnetic recording medium.

The present invention provides a substrate for a magnetic recording medium in which bulges are hardly formed on a surface thereof by a physical impact in a size for a 3.5-inch type HDD, and a width of displacement caused by fluttering is small. The substrate for a magnetic recording medium includes an Al alloy substrate and a Ni alloy plating film formed on a surface of the Al alloy substrate, and has a diameter of 95 to 98 mm, a disk shape having a hole whose inner diameter ranges from 19 to 26 mm in the center thereof, a thickness of 0.48 to 0.64 mm, and a mass of 9.0 to 15.0 g. The Al alloy substrate has a Young's modulus (E) of 74 GPa or more, a density () of 2.75 g/cm.sup.3 or less, and a ratio (E/) of 27 or more between the Young's modulus (E) and the density (). The Ni alloy plating film has a thickness of 4 to 7 m, and when an indentation is formed by pressing a diamond indentor whose tip has a square pyramid shape against a surfaces of the Ni alloy plating film with a test force of 0.49 N for 10 seconds in a vertical direction, an average height of bulges generated around the indentation ranges from 10 to 50 nm.

What is provided is an aluminum alloy substrate for a magnetic recording medium which has high rigidity and an excellent plating properties. The aluminum alloy substrate for a magnetic recording medium has a constitution in which coarse grains whose average grain size is within a range that exceeds 2 m and is less than or equal to 20 m are dispersed, the average number of coarse grains per area of 0.042 mm.sup.2 is 100 or more, and a surface roughness Ra is less than or equal to 0.2 m.

The present invention provides a substrate for a magnetic recording medium in which bulges are not easily formed on a surface thereof by a physical impact in a size for a 2.5-inch type hard disk drive, and a width of displacement caused by fluttering is small. The substrate for a magnetic recording medium includes an Al alloy substrate and a Ni alloy plating film formed on a surface of the Al alloy substrate, has a diameter of 54 to 70 mm, and a disk shape having a hole whose inner diameter ranges from 19 to 26 mm in the center thereof. The Al alloy substrate has a Young's modulus (E) of 74 GPa or more, a density () of 2.75 g/cm.sup.3 or less, and a ratio (E/) of 27 or more between the Young's modulus (E) and the density (). The Ni alloy plating film has a thickness of 4 to 7 m, and when an indentation is formed by pressing a diamond indentor whose tip has a square pyramid shape against a surface of the Ni alloy plating film with a test force of 0.49 N for 10 seconds in a vertical direction, an average height of bulges generated around the indentation ranges from 10 to 50 nm.

A base for a magnetic recording medium, includes a substrate made of an Al alloy and having a surface, and a film made of a NiWP-based alloy and plated on the surface of the substrate. The film includes W in a range of 15 mass % to 22 mass %, P in a range of 3 mass % to 10 mass %, and Pb in a range of 0.03 mass % to 0.08 mass %. The film has a thickness of 5 m or greater.

A sputtering target material, wherein the strength of a sputtering target material can be enhanced without using pure Ta to prevent cracking during sputtering and generating particles and to suppress an irregular composition of a sputtered film, is provided. The present invention provides a sputtering target material containing, in at %, 35% to 50% of Ta with the balance being Ni and an inevitable impurity, wherein the sputtering target is composed only of a Ni.sub.2Ta compound phase and a NiTa compound phase, and a microstructure in each of the Ni.sub.2Ta compound phase and the NiTa compound phase has a maximum inscribed circle diameter of not more than 10 m.

An aluminum alloy disc blank for a magnetic disc made of an aluminum alloy containing Mg: 3.40 to 3.90 mass % with the balance being A1 and inevitable impurities, wherein a conductivity of the aluminum alloy disc blank is 36.0% IACS or higher.

An aluminum alloy substrate for a magnetic disc is made of an aluminum alloy, containing Fe: 1.80 mass % or less, Mn: 0.70 mass % or less, Ni: 2.50 mass % or less, Si: 2.50 mass % or less, Cu: 1.00 mass % or less, Zn: 0.48 mass % or less and Mg: 1.00 to 3.50 mass %, wherein a total content of Fe, Mn and Ni is 1.60 to 4.50 mass % and a mass ratio of Cu/Zn is 0.01 to 0.35 or 6.00 to 50.00, with a balance being Al and inevitable impurities.

A tape-shaped magnetic recording medium includes a substrate; and a magnetic layer that is provided on the substrate and contains a magnetic powder. An average thickness of the magnetic layer is not more than 90 nm, an average aspect ratio of the magnetic powder is not less than 1.0 and not more than 3.0, the coercive force Hc1 in a vertical direction is not more than 3000 Oe, the coercive force Hc1 in the vertical direction and a coercive force Hc2 in a longitudinal direction satisfy a relationship of Hc2/Hc10.8, and a value of 1.5-0.5 is not more than 0.6 N in a tensile test of the magnetic recording medium in the longitudinal direction, where 0.5 is a load at an elongation rate of 0.5% in the magnetic recording medium and 1.5 is a load at an elongation rate of 1.5% in the magnetic recording medium.