There are provided: an aluminum alloy substrate for a magnetic disk, the aluminum alloy substrate including an aluminum alloy including 0.4 to 3.0 mass % of Fe and the balance of Al and unavoidable impurities, in which second phase particles having a longest diameter of 0.5 μm or more and less than 2.0 μm are dispersed at a distribution density of 5000 particles/mm.sup.2 or more; a method for producing the same; and a magnetic disk using the aluminum alloy substrate for a magnetic disk.

A non-magnetic substrate for a magnetic disk includes a substrate main body having two opposing main surfaces, and a metal film that is provided on the main surfaces and is made of a material having a loss factor of 0.01 or more. The non-magnetic substrate has a thickness (T+D) of 0.700 mm or less, the thickness (T+D) being the sum of a thickness T of the substrate main body and a thickness D of the metal film, and a ratio D/T of the thickness D of the metal film to the thickness T of the substrate main body is 0.025 or more.

Various embodiments of the present disclosure provide a read/write device for a hard-disk memory system. The read/write device includes a fixed structure; a membrane region including a first and a second membrane, which are constrained to the fixed structure, and a central portion, interposed between the first and second membranes; a first and a second piezoelectric actuator, mechanically coupled, respectively, to the first and second membranes; and a read/write head, which is fixed to the central portion of the membrane region. The first and second piezoelectric actuators can be controlled so as to cause corresponding deformations of the first and second membranes, said deformations of the first and second membranes causing corresponding movements of the read/write head with respect to the fixed structure.

There are provided: an aluminum alloy substrate for a magnetic disk, the aluminum alloy substrate including an aluminum alloy including 0.4 to 3.0 mass % (hereinafter, %) of Fe, less than 0.10% of Si, less than 0.10% of Mg, and the balance of Al and unavoidable impurities, in which an AlFe-based intermetallic compound having a longest diameter of 2 m or more and less than 3 m is dispersed at a distribution density of 1000 particles/mm.sup.2 or more, and a MgSi-based intermetallic compound having a longest diameter of 1 m or more is dispersed at a distribution density of 1 particle/mm.sup.2 or less; a method for producing the same; and a magnetic disk in which an electroless NiP plating treatment layer and a magnetic layer thereon are disposed on a surface of the aluminum alloy substrate for a magnetic disk.

A magnetic disk substrate is composed of an aluminum alloy substrate, a base plating layer on a surface of the aluminum alloy substrate, and a boundary region between the aluminum alloy substrate and the base plating layer. The boundary region includes a specific boundary region (D(1).sub.I((50-84)) having A, emission intensities equal to 50% to 84% of an average Al emission intensity in an interior region of the aluminum alloy substrate in glow discharge optical emission spectroscopy in the depthwise direction from the surface of the magnetic disk substrate. The specific boundary region (D(1).sub.I(50-84)) has a maximum Fe emission intensity (I(1).sub.Fe(max)) higher than an average Fe emission intensity (I(1).sub.Fe(ave)) in the interior region of the aluminum alloy substrate in the glow discharge optical emission spectroscopy.

In one aspect, the present disclosure provides a method for producing an aluminum platter, which can improve the smoothness of the substrate surface before a magnetic layer is formed thereon and can provide a hard disk substrate that can be processed into a medium with a high yield. In another aspect, the present disclosure relates to a method for producing an aluminum platter, including the following steps 1 and 2: step 1: bringing a composition containing a compound (component A) that has at least one structure represented by the following formula (I) and has a molecular weight between 50 and 100,000 inclusive into contact with a substrate surface of a NiP plated aluminum alloy substrate; and step 2: forming a magnetic layer on the substrate obtained in the step 1.

##STR00001##

An aluminum alloy substrate (1) for magnetic disk satisfies at least two of three inequalities of an inequality group [A] and satisfies all of four inequalities of an inequality group [B], or satisfies at least two of the three inequalities of the inequality group [A] and satisfies all of four inequalities of an inequality group [C], when a plate thickness of the disk at a position (b1) is defined as t.sub.b1, a plate thickness at a position (b2) is defined as t.sub.b2, a plate thickness at a position (b3) is defined as t.sub.b3, a plate thickness at a position (a1) is defined as t.sub.a1, a plate thickness at a position (a2) is defined as t.sub.a2, and a plate thickness at a position (a3) is defined as t.sub.a3.

This aluminum alloy substrate for a magnetic recording medium has a metal structure made of an Al alloy having a composition including Si in a range of 18.0% by mass to 22.0% by mass, Fe in a range of 4.0% by mass to 6.0% by mass, Cu in a range of 2.5% by mass to 4.0% by mass, and Mg in a range of 0.8% by mass to 1.5% by mass with a remainder being Al, a primary-crystal Si precipitate having a maximum diameter of 0.5 m or more and an average particle diameter of 2 m or less is dispersed in the metal structure, a diameter is in a range of 53 mm to 97 mm, and a thickness is in a range of 0.2 mm to 0.9 mm.

This substrate for a magnetic recording medium has a metal structure made of an Al alloy having a composition including Si in a range of 28.0% by mass to 32.0% by mass, Cu in a range of 2.5% by mass to 4.0% by mass, and Mg in a range of 0.8% by mass to 1.5% by mass with a remainder being Al, primary-crystal Si particles having a maximum diameter of 0.5 m or more and an average particle diameter of 2 m or less are dispersed in the metallic structure, a diameter of the substrate is in a range of 53 mm to 97 mm, and a thickness of the substrate is in a range of 0.2 mm to 0.9 mm.

This aluminum alloy substrate for a magnetic recording medium has a metal structure made of an Al alloy having a composition including Si in a range of 18.0% by mass to 22.0% by mass, Ni in a range of 5.0% by mass to 8.5% by mass, Cu in a range of 2.5% by mass to 4.0% by mass, and Mg in a range of 0.8% by mass to 1.5% by mass with a remainder being Al, a primary-crystal Si precipitate having a maximum diameter of 0.5 m or more and an average particle diameter of 2 m or less is dispersed in the metal structure, a diameter is in a range of 53 mm to 97 mm, and a thickness is in a range of 0.2 mm to 0.9 mm.