Gradual Charge Order Melting in Bi0.5Ca0.5MnO3 Induced by Ultrahigh Magnetic Fields

We have investigated the magnetization process of Bi0.5Ca0.5MnO3 under ultrahigh magnetic fields. The metamagnetic transition due to the magnetic field-induced charge order melting has been observed. The metamagnetic transition becomes broad and smeared in the field ascending process at low temperatures. However, in the field descending process, a clear metamagnetic transition is observed even at low temperatures. Gradual charge order melting by magnetic field, and its reformation are expected to occur in ascending and descending magnetic fields, respectively. Quenched spatial inhomogeneity of the charge distribution and/or quantum criticality can account for the observed asymmetric broadening of the field induced charge order melting.