Hall Effect on YBa_2(Cu_(1-x)M_x)_3O_y (M=Fe, Co)

摘要

We measured the normal-state Hall effect on the polycrystal of YBa_2(Cu_(1-x)M_x)_3O_y (M=Fe, Co) prepared by two kinds of heat treatments. The synthesized YBa_2(Cu_(1-x)M_x)_3O_y (M=Fe, Co) was slowly cooled from 890 deg C in air. Some of them were annealed below 400 deg C in O_2 gas (sample (O)_s). The others were heated at 800 deg C in N_2 gas followed by annealing below 400 deg C in O_2 gas (sample (NO)_s). It is considered that there is a difference in the configuration of substituent in the Cu1-O planes between (O)_s and (NO)_s: in (O)_s the substituent is randomly located, while in (NO)_s that makes clusters. The carrier density n_H of (O)_s and (NO)_s in YBa_2(Cu_(1-x)Co_x)_3O_y system decreases with an increase of x. In the case of YBa_2(Cu_(1-x)M_x)_3O_y system, n_H of (O)_s decreases with an increase of x, while that of (NO))_s is almost constant independent of x. The difference in the behavior of n_H between YBa_2(Cu_(1-x)M_x)_3O_y and YBa_2(Cu_(1-x)M_x)_3O_y systems seems to be due to the difference of the microscopic structure around the substituent.