Liquid-to-Liquid Transition in a Spin Model on the Pyrochlore Lattice

One of the foremost goals in the study of pyrochlore magnetism is the search for spin-liquid phases composed of highly-disordered yet strongly correlated states. These phases are usually found in Hamiltonians possessing a highly degenerate ground state manifold preventing the onset of long-range order. However, this degeneracy does not guarantee the realization of a low-temperature spin-liquid as the phenomenon known as order-by-disorder may collapse the system into a long-range ordered phase by selecting entropically favorable spin configurations. In this work, we present a spin model on the pyrochlore lattice that realizes a novel classical spin-liquid at intermediate temperatures, collapsing into another spin-liquid phase at low temperatures. We argue that the rapid crossover between both phases has an entropic origin, providing the first realization of an order-by-disorder selected spin-liquid.