Shear elasticity and spontaneous twisting of the improper ferroelastic crystal K2Ba(NO2)4

Using a torsion pendulum, the peculiarities of low-frequency shear elastic and anelastic properties of the improper ferroelastic crystal K2Ba(NO2)4 have been investigated for various crystallographic oriented samples at a temperature range in the vicinity of the phase transition point (TC = 420 K). The work gives insights into the nature of the internal friction and spontaneous torque arising in the samples at the Curie point.