Rod magnets inscribed in an elastic cuboid: interpreting single-domain ferroics in Onsager's spirit

Abstract

A toy model for ferroic orders through entropy. As the rod/spin concentration (or the volume enclosing the ferroic rods) is variable by a tunable force conjugate to the order parameter, the model exhibits hysteresis associated to some discontinuous isotropic-nematic transitions explained essentially by Onsager's hard-rod model. The uniaxial anisotropy and nonperiodicity by construction is reminiscent of Stoner-Wohlfarth's single-domain magnet, and the toy model may ultimately be seen as a minimalistic for hard ferroics with some possible self-averaging disorders. Spin togglings shall be reliable due to the clean two-well energy landscapes in the athermal transition theory.