AC Wien effect in spin ice, manifest in non-linear non-equilibrium   susceptibility
  We predict the non-linear non-equilibrium response of a "magnetolyte", the Coulomb fluid of magnetic monopoles in spin ice. This involves an increase of the monopole density due to the second Wien effect---a universal and robust enhancement for Coulomb systems in an external field---which in turn speeds up the magnetization dynamics, manifest in a non-linear susceptibility. Along the way, we gain new insights into the AC version of the classic Wien effect. One striking discovery is that of a frequency window where the Wien effect for magnetolyte and electrolyte are indistinguishable, with the former exhibiting perfect symmetry between the charges. In addition, we find a new low-frequency regime where the growing magnetization counteracts the Wien effect. We discuss for what parameters best to observe the AC Wien effect in Dy$_2$Ti$_2$O$_7$. 
Vojt\v{e}ch Kaiser, Steven T. Bramwell, Peter C.W. Holdsworth,   Roderich Moessner
cond-mat.stat-mech cond-mat.str-el