摘要: The pyrochlore iridate Gd2Ir2O7 has been investigated by means of the electron paramagnetic
resonance (EPR) spectroscopy. A magnetic transition at T¤ » 20 K is found in addition to the
transition at TC » 130 K, which has not been reported previously. The phase transition at TC,
which corresponds to a resistivity transition, is resulted from the long-range spin ordering of Ir4+
ions in all-in/all out state. However, the magnetic transition at T¤, which is regardless of resistivity
transition, is not caused by Ir4+ but Gd3+ ions. Both of the magnetic transitions are irrelevant to
the lattice distortion. We suggest that the competition between the enhanced paramagnetism of
Gd3+ ions and the f ¡ d interaction should be responsible for the magnetic transition at T¤.