Single-crystal elastic constants of Co-Al and Co-Fe spinels

The elastic stiffness moduli of single-crystals CoAl2O4, a normal spinel, and CoFe2O4, an inverse spinel, have been determined by an ultrasonic method. The measured values are: C11=290.5, C12=170.3 and C44=138.6 GPa for CoAl2O4, and C11=257.1, C12=150.0 and C44= 85.3 GPa for CoFe2O4. The elastic constants are compared with previously published data of other spinel single crystals and the results show that the cation valence and cation distribution have little influence on the elastic properties of the spinel materials.