Continuous Transition between Antiferromagnetic Insulator and   Paramagnetic Metal in the Pyrochlore Iridate Eu2Ir2O7
  Our single crystal study of the magneto-thermal and transport properties of the pyrochlore iridate Eu2Ir2O7 reveals a continuous phase transition from a paramagnetic metal to an antiferromagnetic insulator for a sample with stoichiometry within ~1% resolution. The insulating phase has strong proximity to an antiferromagnetic semimetal, which is stabilized by several % level of the off-stoichiometry. Our observations suggest that in addition to electronic correlation and spin-orbit coupling the magnetic order is essential for opening the charge gap. 
Jun J. Ishikawa, Eoin C. T. O'Farrell, Satoru Nakatsuji
cond-mat.str-el