Paramagnetism-Ferromagnetism Phase Transition in a Dyonic Black Hole
  Coupling an antisymmetric tensor field to the electromagnetic field in a dyonic Reissner-Nordstr\"om-AdS black hole background, we build a holographic model for the paramagnetism/ferromagnetism phase transition. In the case of zero magnetic field, the time reversal symmetry is broken spontaneously and spontaneous magnetization happens in low temperature. The critical exponents are in agreement with the ones from mean field theory. In the case of nonzero magnetic field, the model realizes the hysteresis loop of single magnetic domain and the magnetic susceptibility satisfies the Curie-Weiss law. 
Rong-Gen Cai, Run-Qiu Yang
hep-th cond-mat.str-el gr-qc