Spontaneous magnetostriction effects in the chiral magnet CrNb3 S6

We identified the spontaneous magnetostriction effects in the chiral magnet CrNb3S6 with the Dzyaloshinskii-Moriya interaction. The powdered x-ray diffraction patterns indicate a prominent magnetostriction effect at the earth field. The unit-cell volume remains almost constant, as in the so-called Invar effect, below 170 K in the paramagnetic region, where the atomic positions of Nb and S show characteristic changes. Below the magnetic ordering temperature of 127 K, the lattice constants a and c exhibit an opposite temperature dependence. When a finite magnetic field of 1.2 kOe is applied, a magnetostriction appears that counterbalances the spontaneous magnetostriction. The magnetostriction phenomena in CrNb3S6 were investigated from the viewpoint of the atomic level of the chiral effect.