Negative Thermal Expansion and Spin Ices

Relaxation of the Chemical Bond, Springer Series in Chemical Physics 108, DOI 10.1007/978-981-4585-21-7 42, Springer Science+Business Media Singapore 2014 

The problem of the frustrated Ising antiferromagnet on a (pyrochlore) lattice of comer-shared tetrahedra has been related to the water ice problem [14]. Spin ice materials are characterized by disorder of magnetic ions even when said ions are at very low temperatures. AC magnetic susceptibility measurements find evidence for a dynamical freezing of the magnetic moments as the temperature is lowered somewhat below the temperature at which the specific heat displays a maximum. 

According to the current understanding, replacement of the HT proton with an ion of nonzero spin and the associated ion-ion and spin-spin interaction adding to the short-range interaction may discriminate spin ices from other magnetic materials. The short-range interactions and the repulsion between electron pairs on adjacent oxygen ions may also play the same roles as they do in water and ice. 

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