Abstract: It is an object of the present invention to provide a permanent magnet which is observed as a uniform structure without microstructures, but shows a pinning type initial magnetization curve. There is provided a rare earth permanent magnet comprising a magnetic intermetallic compound comprising R, T, N and an unavoidable impurity, wherein R is one or more rare earth elements comprising Y, T is two or more transition metal elements and comprises principally Fe and Co; wherein the magnetic intermetallic compound has an T/R atomic ratio of 6 to 14; a magnetocrystalline anisotropy energy of at least 1 MJ/m3; a Curie point of at least 100° C.; average particle diameter of at least 3 ?m; and a substantially uniform structure; wherein the rare earth permanent magnet has a structure that gives a pinning-type initial magnetization curve; and wherein the magnetic intermetallic compound has a Th2Zn17-type structure, and the like.

Abstract: A bulk anisotropic rare earth permanent magnet consists essentially of R, Fe or Fe and Co, and N, wherein R is selected from rare earth elements inclusive of Y and contains Sm as a main component, and has a primary phase of Th2Zn17 type rhombohedral crystal structure, a density of at least 90% of the true density, and unidirectionally oriented C-axis. By electric conduction hot pressing of SmFeN base powder under rapid heating and rapid cooling conditions, the powder can be worked into the anisotropic bulk magnet without decomposing the 2-17 phase.

Abstract: Provided is a highly efficient method for manufacturing preferably a small diameter substrate for a magnetic recording medium. More specifically, provided is a method for manufacturing a substrate for a magnetic recording medium, comprising a step of coring for obtaining a plurality of doughnut-shaped substrates having a diameter at most 65 mm from a monocrystalline silicon wafer having a diameter at least 150 mm and at most 300 mm, wherein coring of an inner diameter and an outer diameter are carried out by different means. In said step of coring said coring of the inner diameter is preferably carried out by water jet cutting or laser cutting.

Abstract: Provided is a substrate for a magnetic recording medium, preferably a substrate having a small diameter of not more than 65 mm, which is advantageous in respect of physical properties and cost. More specifically, provided is a substrate for a magnetic recording medium, using a monocrystalline silicon wafer which has been heated and/or etched at least once before. Moreover, provided is a method for manufacturing a substrate for a magnetic recording medium, the method comprising a step of coring for obtaining a plurality of doughnut-shaped substrates having an outer diameter of not more than 65 mm from a monocrystalline silicon wafer having a diameter of at least 150 mm and at most 300 mm which has undergone heating and/or etching at least once. The method may preferably further comprise a step of chamfering for removing edges of inner and outer circumferential faces of said doughnut-shaped substrate; and a step of circumferential face-polishing for polishing the chamfered inner and outer circumferential faces.

Abstract: Provided is a method for improving the productivity of a coring step. More specifically, provided is a method for manufacturing a substrate for a magnetic recording medium substrate, comprising a step of coring for obtaining a plurality of doughnut-shaped substrates having a diameter of at most 55 mm from a monocrystalline silicon wafer of a diameter having at least 150 mm and at most 300 mm, wherein the coring is performed such that a leftover wafer excluding the plurality of substrates remains in one piece. In said step of coring, the coring is preferably performed using a laser cutting or a water jet cutting such that said minimum width of said surface of said leftover wafer is 1.5 to 2.5 times the thickness of the wafer.

Abstract: The present invention provides a magnetron sputtering system, which ensures a formation of a desired thin film, using a thick target. In the sputtering process, a portion of the target does not have erosion free portions. The present invention provides a magnetron sputtering system comprising a chamber for sputtering, a target electrode 5 installed inside said chamber, a substrate electrode 6 installed in the chamber opposite to the target electrode, a ring-shaped magnet 2 installed so as to enclose the side surface of the target electrode, and a semi-circular disk shaped magnet installed opposite to the target-mounted surface of the target electrode, wherein the semi-circular disk shaped magnet is rotated in the circumferential direction of the target electrode and is magnetized in the direction perpendicular to the target electrode. This ensures a specific magnetic field component to be generated over the thick planar target surface 3.

Abstract: Disclosed is a rare earth-based sintered permanent magnet block used in the rotor of a permanent magnet synchronous motor. The magnet block of the form having an upper surface and a lower surface in parallel is provided in each of the upper and lower surfaces with at least one narrow slit having a specified incision depth, width and length so as to decrease the adverse influences of the eddy currents generated in the magnet block while the running direction of the slits in the upper surface and the running direction of the slits in the lower surface make an angle of at least 10° or, preferably, 90° so that the decrease in the bending strength of the magnet block due to the slits can be minimized without decreasing the desired eddy current-decreasing effect.

Abstract: Disclosed is a magnetically anisotropic rare earth-based permanent magnet having a nanocomposite structure consisting of fine dispersion of a magnetically hard phase, e.g., Nd2Fe14B, in alignment relative to the easy magnetization axis, a magnetically soft phase and a non-magnetic phase having a melting point lower than those of the magnetically hard and soft phases. The permanent magnet is prepared in a process in which a quenched thin magnet alloy ribbon having a composition capable of forming a magnetically hard phase, magnetically soft phase and non-magnetic phase by a heat treatment is subjected to a heat treatment in a magnetic field of at least 3 T at a temperature not lower than the melting point of the non-magnetic phase so that the liquid phase formed from the non-magnetic phase serves to facilitate rotating orientation of the magnetically hard grains to be aligned in the direction of the magnetic field relative to the easy magnetization axis.

Abstract: A bulk anisotropic rare earth permanent magnet consists essentially of R, Fe or Fe and Co, and N, wherein R is selected from rare earth elements inclusive of Y and contains Sm as a main component, and has a primary phase of Th2Zn17 type rhombohedral crystal structure, a density of at least 90% of the true density, and unidirectionally oriented C-axis. By electric conduction hot pressing of SmFeN base powder under rapid heating and rapid cooling conditions, the powder can be worked into the anisotropic bulk magnet without decomposing the 2-17 phase.

Abstract: The present invention provides a magnetron sputtering system, which ensures a formation of a desired thin film, using a thick target. In the sputtering process, a portion of the target does not have erosion free portions. The present invention provides a magnetron sputtering system comprising a chamber for sputtering, a target electrode 5 installed inside said chamber, a substrate electrode 6 installed in the chamber opposite to the target electrode, a ring-shaped magnet 2 installed so as to enclose the side surface of the target electrode, and a semi-circular disk shaped magnet installed opposite to the target-mounted surface of the target electrode, wherein the semi-circular disk shaped magnet is rotated in the circumferential direction of the target electrode and is magnetized in the direction perpendicular to the target electrode. This ensures a specific magnetic field component to be generated over the thick planar target surface 3.

Abstract: Disclosed is a magnetically anisotropic rare earth-based permanent magnet having a nanocomposite structure consisting of fine dispersion of a magnetically hard phase, e.g., Nd2Fe14B, in alignment relative to the easy magnetization axis, a magnetically soft phase and a non-magnetic phase having a melting point lower than those of the magnetically hard and soft phases. The permanent magnet is prepared in a process in which a quenched thin magnet alloy ribbon having a composition capable of forming a magnetically hard phase, magnetically soft phase and non-magnetic phase by a heat treatment is subjected to a heat treatment in a magnetic field of at least 3 T at a temperature not lower than the melting point of the non-magnetic phase so that the liquid phase formed from the non-magnetic phase serves to facilitate rotating orientation of the magnetically hard grains to be aligned in the direction of the magnetic field relative to the easy magnetization axis.

Abstract: Disclosed is a method for the preparation of a magnetically anisotropic rare earth/iron/boron-based permanent magnet in a relatively bulky form having a nanocomposite structure as prepared from quenched thin ribbons of the alloy. The method comprises heating the powder of quenched thin ribbons to a temperature allowing partial formation of a liquid phase of a lanthanum/iron or rare earth/copper alloy of low melting point and subjecting the powder of the quenched thin ribbons to a uniaxial hot-deformation treatment by passing the powder under resistance heating through a gap between a pair of compression rollers.

Abstract: Disclosed is a novel magnetically anisotropic rare earth-based permanent magnet having a nanocomposite structure consisting of a hard magnetic phase such as Nd2Fe14B and a soft magnetic phase such as bcc-iron, Fe3B and Fe2B in a volume ratio of 10:90 to 90:10 uniformly dispersed each in the other in a fineness of a few tens nanometers, in which particles of the hard magnetic phase are aligned in a direction relative to the easy magnetization axes of the particles. Such an anisotropic permanent magnet can be prepared by the method comprising: preparing a starting amorphous alloy of a composition susceptible to dispersion precipitation of the hard magnetic phase, for example, by the melt-spun method; forming the amorphous alloy into a magnet block; heating the magnet block at 600 to 1000° C.

Abstract: Disclosed is a rare earth-based, magnetically anisotropic permanent magnet material consisting of a rare earth element, e.g., neodymium or praseodymium, iron optional in combination with cobalt and boron and having excellent magnetic properties by virtue of the magnetic coupling between the magnetically hard and soft phases. The magnet material has a structure consisting of crystalline particles of, e.g., Nd.sub.2 Fe.sub.14 B, having a particle diameter of 1 .mu.m or larger and fine crystals of iron of submicron size in a rod-shaped or platelet form precipitated within each crystalline particle of Nd.sub.2 Fe.sub.14 B. This magnet material can be prepared by several different methods including, for example, a solid phase reaction of an intermetallic compound of Nd.sub.2 Fe.sub.17 with boron to effect a double decomposition reaction producing Nd.sub.2 Fe.sub.14 B and iron.

Abstract: Disclosed is a novel composite magnet assembly for an insertion device of the Halbach type or hybrid type to be inserted into the linear part of, for example, an electron accelerator to generate a sine-curved periodical magnetic field in the air gap between two oppositely facing composite magnet block arrays. Different from a conventional magnet block assembly consisting of a plurality of permanent magnet blocks or alternate assembly of permanent magnet blocks and soft-magnetic pole pieces, the inventive magnet block assembly is composed of a plurality of oppositely facing composite magnet blocks each formed with a single base magnet block provided with a plurality of slits into which insert magnet pieces or insert pole pieces are inserted so that the dimensional accuracy in the length-wise direction of the magnet block assembly can be greatly decreased to improve the regularity of the periodical magnetic field.

Abstract: Provided by the invention is a method for the preparation of a magnetically anisotropic permanent magnet mainly consisting of crystallites of the Nd.sub.2 Fe.sub.14 B phase. The method comprises the steps of:(a) preparing an amorphous alloy of neodymium, iron and boron in molar fractions corresponding to the Nd.sub.2 Fe.sub.14 B phase or a nanocomposite of the Nd.sub.2 Fe.sub.14 B/Fe.sub.3 B or Nd.sub.2 Fe.sub.14 B/Fe system, for example, by the melt-spun method; and (b) subjecting the amorphous alloy of neodymium, iron and boron to a heat treatment in a magnetic field of at least 3 T (tesla) at a temperature in the range from 550 to 800.degree. C. for a length of time in the range from 1.times.10.sup.2 to 1.times.10.sup.4 seconds in an atmosphere of a non-reactive gas or vacuum.

Abstract: Proposed is an improvement in an opposed-magnet magnetic circuit assembly with permanent magnets suitable for use, for example, in an MRI instrument comprising a pair of upper and lower permanent magnets to form a magnetic-field gap space therebetween, a pair of magnetic-field adjustment plates each on the surface of the permanent magnet to face the gap space and a pair of back yokes each on the back surface of the permanent magnet. According to the first aspect of the invention, a combination of a gradient coil and a shimming plate is mounted on the magnetic-field adjustment plate with intervention of several pieces of shim members and, further, another set of second shim members are bonded to the surface of the shimming plate facing the gap space with an object to improve the uniformity of the magnetic field in the gap space.

Abstract: Disclosed is a method for the preparation of a novel composite rare earth-based magnetically anisotropic sintered permanent magnet in which: (a) a base alloy consisting of a host phase of R.sub.2 T.sub.14 B (R: a rare earth element; T: iron or a combination of iron and cobalt) having a particle diameter of 2 to 10 .mu.m and containing in each particle a phase rich in the content of T and having a particle diameter not exceeding 1 .mu.m is prepared by the strip casting method; (b) the base alloy is crushed; (c) the base alloy powder is blended in a specified proportion with a powder of an auxiliary alloy of R-T or R-T-B in a specified proportion; (d) the powder blend is subjected to further comminution; (e) the comminuted powder blend is subjected to compression-molding in a magnetic field into a powder compact; and (f) the powder compact is sintered by a heat treatment.

Abstract: Proposed is an improvement in an opposed-magnet magnetic circuit assembly with permanent magnets suitable for use, for example, in an MRI instrument comprising a pair of upper and lower permanent magnets to form a magnetic-field gap space therebetween, a pair of magnetic-field adjustment plates each on the surface of the permanent magnet to face the gap space and a pair of back yokes each on the back surface of the permanent magnet. According to the first aspect of the invention, a combination of a gradient coil and a shimming plate is mounted on the magnetic-field adjustment plate with intervention of several pieces of shim members and, further, another set of second shim members are bonded to the surface of the shimming plate facing the gap space with an object to improve the uniformity of the magnetic field in the gap space.

Abstract: The present invention provides is an improvement in a magnetic circuit system with a pair of opposite permanent magnets to construct an MRI instrument comprising a pair of upper and lower permanent magnets connected with yokes to form an air gap space therebetween, in which the patient under MRI inspection is kept lying, a pair of shimmed pole pieces each mounted on the permanent magnet to face the air gap and a pair of gradient coils each mounted on the shimmed pole piece to face the air gap. The improvement comprises mounting a cancellation magnetic plate, which is a thin plate of a magnetic material having a coercive force of 0.1 to 500 Oe, on the gradient coil to face the air gap with an object to cancel the residual magnetization of the shimmed pole piece by the gradient magnetic field. The cancellation magnetic plate has a thickness not exceeding 0.5 mm and has a base area which is 5 to 75% relative to the base area of the gradient coil.