ANOMALY ON THE TEMPERATURE-DEPENDENCE OF THE HALL RESISTANCE IN SEMICONDUCTING YBA2CU3O6+X FILMS

The Hall effect has been studied in semiconducting YBa2Cu3O6+x films u nder equilibrium conditions and also after illumination with visible l ight. A rounded maximum is observed on the temperature dependence of t he Hall resistance, R(xy)(T). This anomaly shifts down the temperature scale as the density of free carriers increases, because of an increa se in the oxygen content x and also because of a photoexcitation of mo bile holes (a frozen photoconductivity). It is suggested that the maxi mum observed on the R(xy)(T) curves stems from the appearance of an an tiferromagnetic order.