Magnetic phase diagrams of electron-doped high-T_c cuprates Pr_1-xLaCe_xCuO_4-δ and Nd_2-xCe_xCuO_4-δ studied by μSR measurements

Magnetic phase diagrams of electron-doped high-temperature superconducting (SC) cuprates Nd_2-xCe_xCuO_4-δ (NCCO) and Pr_1-xLaCe_xCuO_4-δ (PLCCO) has been studied by means of muon spin relaxation and rotation (μSR) measurements. Two characteristic temperatures T_N1 and T_N2 are defined in the zero-field μSR (ZF-μSR) measurements for both NCCO and PLCCO. Below T = T_N1, which approximately corresponds to the previously reported Néel temperature, an exponential type muon spin relaxation firstly appears in the time spectra and upon cooling below around T_N2 another faster component of relaxation or muon spin rotation is observed similarly. Although critical concentration for the bulk superconductivity is different between the two systems, antiferromagnetic (AF) phase contacts with the SC phase partially overlapping in both systems and AF phase is suddenly reduced in the appearance of SC phase, suggesting a competition between superconductivity and AF order. Our quantitative analyses of the AF volume fraction clearly demonstrate this.