Metal insulator transition induced by magnetic field in GdTe

Among various ground states of rare earth monotelluride, bulk GdTe is metallic with antiferromagnetic order (AFM) at low temperature. We grow GdTe thin films by molecular beam epitaxy (MBE) and study their properties by scanning tunneling microscopy (STM) and magnetic property measurement. Density of states (DOS) obtained by STM exhibits insulating gap, which can be closed by magnetic field for certain film thicknesses, indicating a transition from insulator to metal. The gap size can be as large as 30 meV and closed by relatively weak magnetic field of 2.6 T for 6 layers of GdTe. We attribute the observed effects to the exchange interaction between d and f electrons.