Measurements of the elastic stiffness constants of single-crystal SmCo5 and of liquid-phase sintered SmCo5 permanent magnet material

Abstract

The five elastic stiffness constants were determined for both single-crystal SmCo5 and for the commercially processed liquid-phase sintered (LPS) SmCo5 permanent magnet material. The LPS material is an aligned polycrystalline aggregate of SmCo5 crystallites oriented so that their magnetically easy c axes are approximately parallel. The elastic constants were obtained from the velocities of propagation of ultrasound in various directions in samples of known thickness and density. For the single crystal, the room-temperature values of the constants (in units of 1012 dyn/cm2) are c11=1.968±2%, c12=1.032±4%, c13=1.049±4%, c33=2.398±2%, and c44=0.483±2%, and for the LPS permanent magnet material, c11=1.330±2%, c12=0.616±5%, c13 =0.485±5%, c33=1.659±2%, and c44=0.419±2%. The decrease in elastic constants in SmCo5 relative to cobalt can be related qualitatively to a corresponding decrease in the number of nearest-neighbor cobalt bonds in SmCo5.