Powerful bonded nonconducting permanent magnet for downhole use

Abstract From the Canadian patent

A transverse dipole NMR tool includes a non-conductive permanent magnet (103) made of electrically conductive material such as AmCo. The concentration of SmCo is selected to be at a level low enough to prevent the formation of an electrically conductive path through the magnet. Disposed between the grains of conductive magnet material (101) may be either a ferrite (to increase the remnant magnetization and coercive force) or an inert material. There is a tradeoff between increasing the grain size of the conductive material and the increased intragranular power dissipation. The volume fraction of the conductive material may be increased to a level somewhat higher than a theoretical …