Magnetization and magnetostriction of NiFe$_{2-x}$Sc$_x$O$_4$ spinels

The specific magnetization and the constants of magnetostriction $\lambda_{100}$ and $\lambda_{111}$ of three monocrystals of the system NiFe$_{2-x}$Sc$_x$O$_4$ (x = 0,05; 0.12; and 0.3) are measured in a temperature range of 4.2 K to the Curie point. An anomalous increase in the constants $|\lambda_{100}|$ and $|\lambda_{111}|$ is observed in a temperature range from 77 to 4.2 K. The concentration relation of $\lambda_{111}(x)$ is linear at all temperatures, while that of $\lambda_{100}(x)$ is linear at room temperature but is not linear at lower temperatures.