A new class of Sm-TM magnets for operating temperatures up to 550 degrees C

A breakthrough has been made for magnets to be used at high temperatures. A new class of Sm(CowFevCuwZry)(x) type magnets with linear demagnetization curves up to 550 degreesC has been developed. A new symbol, T-M, is introdu ced, which is defined as the maximum temperature at which the induction dem agnetization curve of a magnet is a straight line, Magnet in this class can be made with its own unique T-M There is a direct relationship between the optimum Co content and T-M An equation has been established to relate the Co content and the T-M Using the equation, magnets can be provided with the best combination of highest (BH)(max) and a linear demagnetization curve f or any application with a specified operating temperature, These magnets ha ve high resistance to thermal demagnetization because of their low temperat ure coefficients of H-i(c) which result in a higher H-i(c) at high temperat ure. Thermal stability of these magnets at 300-550 degreesC has been studie d, showing that the loss due to metallurgical changes is <2% for new magnet s at 550<degrees>C for 360 hr, Experiment confirms that coated magnets can be expected to have considerable life expectancy and relatively low magneti c losses at the intended T-M, Experiment also shows that, at high temperatu res, the magnetic pinning strength in the magnets increases as the T-M incr eases, TEM microstructures for some magnets have been studied. Magnets with higher T-M have smaller cell sizes and larger volume of cell boundaries th an conventional 2:17 magnets, It is believed that the large volume of cell boundaries plays a role in the high resistance to thermal demagnetization.