In an embodiment, elements 620a are made of the aforementioned strongly magnetic materials. Elements 620a are typically pre-magnetized with specific values for the components of magnetic moment. The shape of element 620a may be cylindrical, as shown in FIG. 3, or some other shape such as a sphere, an ellipsoid, a cuboid, or a polygonal prism.

Element 620c typically has a different phase from element 620a. For example, it may have the same material composition and geometric shape as element 620a, but differ in one or more components of the magnetic moment, M. Alternatively, element 620c may consist of a non-ferromagnetic material, such as a ferrimagnetic, paramagnetic, or non-magnetic material, in which case the phase of element 620c differs from that of element 620a, by virtue of its different material composition.

Element 620b fills a gap of length L1 separating element 620a from element 620c; similarly, element 620d fills a gap of length L2 separating element 620c from element 620a of the adjacent segment, as shown in FIG. 6. Often, for thermal stability of MPMR 600, it is preferable that elements 620b and 620d consist of non-magnetic, electrically non-conducting materials which are at least moderately thermally conductive, such as silicon oxide, silicon nitride, or aluminum oxide.