Preferential crystallographic alignment in polycrystalline MnP

The existence of preferential crystallographic alignment in hot pressed and die upset manganese phosphide (MnP) was investigated using magnetic measurements and electron backscatter diffraction (EBSD). Pole figures calculated from the EBSD data show that die upsetting causes the 〈1 1 0〉 directions to align preferentially along the die upset (DU) direction with the 〈0 0 1〉 direction preferentially perpendicular to the DU direction. Magnetic measurements show that the die upsetting can reduce the saturation field relative to that of a similar sample with randomly oriented grains. Since the low-field magnetocaloric effect in single crystals of MnP has been shown to be greatest along the 〈0 1 0〉 direction and smallest along the 〈1 0 0〉 direction, this technique offers a means to achieve the advantages of single crystal alignment with the economy of using bulk processing techniques on polycrystalline material. The peak magnetic entropy change measured with the field applied along the DU direction in the DU sample was 3%, 5%, and 8% greater than the peak entropy change of a randomly oriented powder at fields of 2.0, 1.0, and 0.5 T, respectively.