Exchange field induced large magnetoresistance in the correlated insulator phase of ultrathin Beryllium films

We present a detailed study of low-temperature magnetotransport properties of ultrathin, amorphous Be films in the EuS/Be bilayers. Significant magnetoresistance (MR) of pure insulating Be films can only be observed in fairly high magnetic field ( > ∼5 tesla ), but by depositing insulating ferromagnetic EuS on top of Be film, one can obtain the same value of MR at low magnetic field (∼ 0.2 tesla). We argue that this shift of MR from high field to low field may be caused by the exchange field in the Be component of Be/EuS bilayers.