Effect of constant magnetic field on the microhardness of LiIO$_3$ single crystals

The microhardness of LiIO$_3$ crystals is found to decrease after action of a constant magnetic field $\mathbf{B}$. The maximum change in the microhardness is observed within an hour after the magnetic treatment. Then, the microhardness demonstrates a gradual relaxation return to the initial value. The change in the microhardness is dependent on the orientation of magnetic inductance vector with respect to the polar axis. The effect is pronounced at $\mathbf{B}\perp$ [0001] and is absent at $\mathbf{B}\parallel$ [0001]. The sensitivity of the microhardness of LiIO$_3$ to a constant magnetic field has a threshold character: the effect appears at the magnetic induction higher than 1 T, increases quickly, and reaches the saturation even at 1.3 T. The reversibility of the magnetically induced decrease in the microhardness has been justified: the effect is exactly reproduced during repeated tests after two weeks. The study of the crystals doped with chromium shows that the increase in the Cr concentration enhances the magnetoplastic effect in LiIO$_3$, i.e., favors the softening of the material after the magnetic treatment.