A permanent magnet for an MRI scanner is made by removing extraneous elements from an ore containing rare earth elements to leave elements Pr and Nd therein, and then selectively stripping therefrom a portion of the element Nd as a byproduct to leave an ore residuum including both elements Pr and Nd therein. The residuum is alloyed with a transition metal to form an alloy therewith. The alloy is then formed into a rare earth permanent magnet configured for use in the MRI scanner.
This application is a division of application Ser. No. 09/248,950 filed Feb. 12, 1999 now U.S. Pat. No. 6,377,049, which is hereby incorporated by reference in its entirety.
With a view to providing a magnet apparatus which can form a medium magnetic field with use of permanent magnets, the magnet apparatus having a pair of parallel disc-like permanent magnets with magnetic poles of mutually opposite polarities opposed to each other through a spacing, further comprises: two pairs of rings constituted by permanent magnets and provided respectively on pole faces of the pair of permanent magnets coaxially and doubly, the two pairs of rings each having a magnetizing direction inclined relative to a magnetizing direction of the pair of permanent magnets and having magnetic poles of mutually opposite polarities opposed to each other through a spacing; and two pairs of cylinders formed by a ferromagnetic material and partitioning the interiors of the pair of permanent magnets respectively coaxially and doubly.
