Temperature Dependence of Resistivity of Sintered Rare-Earth Permanent-Magnet Materials

We studied the resistivity of rare-earth permanent-magnet materials over the temperature range -40 degrees C to + 150 degrees C. We investigated three different materials from four manufacturers, including Nd(2)Fe(14)B, SmCo(5), and Sm(2)Co(17), and measured their resistivities and temperature coefficients. We found that rare-earth permanent-magnet materials show an anisotropic resistivity behavior. In fact, the resistivity anisotropy causes larger resistivity difference than the temperature variation within the range studied. In many applications, such as permanent-magnet motors, this behavior has to be taken into account in design.