Abstract: Proposed is an improvement in a magnet assembly of an MRI instrument of the permanent magnet type comprising a pair of permanent magnets facing each other and forming a magnet gap therebetween. A pair of pole pieces each of which are mounted on one of the permanent magnets and a pair of gradient-field coils each of which are mounted on one of the pole pieces where both the pole pieces and coils face the gap. With an object of the invention to cancel the adverse influences caused by the residual magnetization of the pole pieces by the gradient magnetic field generated in the gradient-field coils. The invention proposes providing a pair of magnetic-field compensation members each on one of the gradient-field coils so that the residual magnetization in the compensation members generates a magnetic field which is compensatory for the magnetic field due to the residual magnetization in the pole pieces.

Abstract: The invention provides a cylindrical permanent magnet unit suitable for application to gyrotrons. Essentially the magnet unit consists of two cylindrical permanent magnets which are coaxially aligned, and there is a space between the two cylindrical magnets. Each of the two cylindrical magnet is a coaxially juxtaposed assembly of a plurality of ring-like permanent magnets, and each ring-like magnet is constructed of a plurality of permanent magnet segments. In one of the two cylindrical magnets every ring-like permanent magnet is magnetized in radial directions from the inside toward the outside, and in the other every ring-like permanent magnet is magnetized in radial directions from the outside toward the inside. In the bore of the cylindrical magnet unit the magnetic field is in the direction of the longitudinal center axis of the bore.

Abstract: A permanent magnet arrangement for magnetron plasma processing is disclosed. The arrangement includes a plurality of permanent magnets each of which has a fan-shaped or equilateral cross section parallel to the major surfaces thereof. The permanent magnets are assembled to form the permanent magnet arrangement which takes a disk-like configuration or a polygon. Each of the plural permanent magnets is made of rare-earth material and radially or essentially radially magnetized.

Abstract: The invention relates to an apparatus for producing a magnetic field in a space between two oppositely arranged permanent magnet discs, which is suitable for use in magnetic resonance imaging (MRI). An object of the invention is to reduce the size and weight of the yoke connecting the two permanent magnet discs without causing magnetic saturation of the yoke in view of the fact that magnetic saturation of the yoke leads to the appearance of leakage flux and consequential lowering of the uniformity of the magnetic field. The object is accomplished by regulating the cross-sectional area of the whole magnetic path in the yoke, A.sub.y, such that the following equation holds: A.sub.y =1/a.times.A.sub.m B.sub.m /B.sub.ys, where A.sub.m is the cross-sectional area of magnetic path in each permanent magnet disc, B.sub.m is the magnetic flux density in each permanent magnet disc at normal temperature, B.sub.

Abstract: A highly corrosion-resistant rare earth-, e.g., neodymium-, based sintered permanent magnet is proposed which is characterized by the specific chemical composition of the magnet alloy including cobalt and/or chromium in a specified atomic percentage, by the density of the sintered body of at least 95% of the density of the alloy ingot and by the corrosion-resistant surface film formed on the surface of the sintered body by a specific method. By virtue of the favorable conditions against corrosion including the specific chemical composition of the magnet alloy and the high density of the sintered body, these conditions are also favorable for enhancing the adhesion of the corrosion-resistant coating film to the surface of the sintered body.

Abstract: A rare earth permanent magnet of a composition, Ce(CO.sub.1-x-y-a Fe.sub.x Cu.sub.y M.sub.a).sub.z, where a, x, y, and z are: 0.005<1<0.10; 0.20<x<0.40; 0.10<y<0.30; 4.8<z<6.0; and M is zirconium, titanium, nickel, and/or manganese. A method for manufacturing the magnet is disclosed comprising the steps of: applying a first solid solution heat treatment to an alloy ingot having the above composition at temperatures from 900.degree. to 1100.degree. C. for 10 minutes to 100 hours; pulverizing the alloy ingot; obtaining a magnet body from this pulverized alloy by the powder metallurgy method; sintering the magnet body; applying a second solid solution heat treatment to the sintered magnet body at 900.degree.-100.degree. C. for 10 minutes to 100 hours; and applying aging heat treatment to the sintered magnet.

Abstract: The magnetic properties or, in particular, coercive force of a sintered permanent magnet composed of a light rare earth element, boron and iron can be greatly improved without affecting the residual magnetic flux by the admixture of a relatively small amount of additive elements including heavy rare earth elements, aluminum, titanium, vanadium, niobium and molybdenum. In the inventive magnets, the distribution of the additive element is not uniform but localized in the vicinity of the grain boundaries of the matrix particles. Such a localized distribution of the additive elements is obtain by sintering a powder mixture composed of a powder of an alloy of the base ingredients and a powder containing the additive element or elements.

Abstract: An improved method is proposed for the preparation of a sintered permanent magnet of a rare earth-iron-boron alloy having remarkably improved magnetic properties and stability by the powder metallurgical process. The scope of the inventive method consists in the particle size classification of the alloy powder for compression molding into a powder compact to be sintered, by which particles having a finer particle diameter and, preferably, a coarser particle diameter than the respective critical values are removed so as to effectively prevent oxidation of the too fine particles and improving the magnetic orientation of the particles as well as the sintering behavior of the particles.

Abstract: The invention relates to a method of producing a sintered Nd-Fe-B magnet which has a cylindrical or annular shape and is magnetized in radial directions with polar anisotropic orientation. In a cylindrical mold cavity filled with a Nd-Fe-B magnetic alloy powder a pulse of magnetic field is produced so as to cause polar anisotropic orientation of the magnetic powder with at least six poles distributed around the circumference, and a pulse-like pressure is applied to the powder in the mold cavity to compact the powder into a cylindrically shaped body while the pulse of magnetic field is lasting. The shaped body is sintered, and subsequently the side surface of the sintered body is abraded to remove projecting regions, which are attributed to anisotropic shrinkage during sintering, until the surface becomes accurately cylindrical.

Abstract: A rare earth permanent magnet of the formulaR(Fe.sub.1-x-y Co.sub.x M.sub.y).sub.z,in which R is rare earth element(s) and/or Y, M is Si, Ti, Mo, B, W, V, Cr, Mn, Al, Nb, Ni, Sn, Ta, Zr, and/or Hf, and x, y, z are numbers such that0.ltoreq.x.ltoreq.0.99,0.01.ltoreq.y.ltoreq.0.03, and8.5<z<12.0,and in which the matrix cells consist of two finely segregated phases.

Abstract: Method of preparing an anisotropic permanent magnet by a powder metallurgical technique, in which, the step of orientation of anisotropically magnetic particles during shaping by compression to give a green body prior to sintering, the magnetic field is applied pulse-wise to the mass of magnetic particles and an impacting compressive force is applied to the thus oriented particles in the direction parallel to the magnetic field during the period in which a pulse of the pulse-wise magnetic field is sustained. This method ensures a much higher degree of particle orientation than in the conventional static-field method by virtue of the possibility of obtaining a much stronger magnetic field without problems which otherwise are unavoidable. The principle of the method is applicable to the preparation of a cylindrical or annular permanent magnet magnetizable in a plurality of radial directions.

Abstract: The invention provides a method for producing a magnetic bias field in a magnetic bubble domain memory device. The method comprises coupling a magnetic bubble domain element with a permanent magnet. The permanent magnet is formed of a rare earth metal-containing alloy for use in the bubble domain memory device in respect of the reversible temperature coefficient of the magnet capable of being in compliance with the temperature coefficient of the bubble disappearance field of the memory device. The alloy characteristically contains nickel as an essential component so that the composition of the alloy is expressed by the formulaR(Co.sub.1-x-y Cu.sub.x Ni.sub.y).sub.z,in which R is a rare earth element, e.g. samarium or cerium, and s, y and z are each a positive number from 0.001 to 0.4, from 0.001 to 0.6 and from 4.0 to 9.0, respectively, with the proviso that x+y is smaller than 1.

Abstract: The permanet magnet composed of a rare earth element, e.g. samarium, and cobalt together with iron, copper and some other additive elements and prepared according to the inventive method has a high coercive force and excellent squareness of the magnetic hysteresis loop despite the relatively low content of copper which has been considered to be indispensable for obtaining a high coercive force. The characteristic feature of the inventive method consists in the aging treatment of the sintered body of the alloy powder of a specified composition undertaken in two or more steps, each being carried out by continuously cooling the sintered body within a specified temperature range at a specified cooling velocity.

Abstract: The invention provides a rare earth metal-containing alloy for permanent magnets having a composition expressed by the formulaSm.sub.1-.alpha. Ce.sub..alpha. (Co.sub.1-x-y-u-v-w Fe.sub.x Cu.sub.y Ti.sub.u Zr.sub.v Mn.sub.w).sub.z,in which the suffixes are each a numerical value as defined by:0.1.ltoreq..alpha..ltoreq.0.90;0.10.ltoreq.x.ltoreq.0.30;0.05.ltoreq.y.ltoreq.0.15;0.002.ltoreq.u.ltoreq.0.03;0.002.ltoreq.v.ltoreq.0.03;0.005.ltoreq.w.ltoreq.0.08;with the proviso that 0.01.ltoreq.u+v+w.ltoreq.0.10; and 5.7.ltoreq.z.ltoreq.8.1 . The permanent magnets prepared with the alloy have very high magnetic properties, especially, in the coercive force and the maximum energy product even better than those obtained with a samarium-based alloy along with good machinability as in the cerium-based alloys suitable for mass production.