Temperature-dependence of low-energy spin excitation in electron-doped high-T_c superconductor Pr_{1 - x} LaCe_x CuO₄

We studied the temperature-dependences of low-energy spin fluctuations in electron-doped high-T_c cuprates, Pr_{1 - x} LaCe_x CuO₄ (PLCCO) for both superconducting (SC) and long range antiferromagnetic (AF) ordered phases. We clarified the different thermal evolution of local spin susceptibility χ^″ (ω) between the AF and SC samples. For the former sample (x = 0.07), χ^″ (ω) is nearly temperature-independent in the AF ordered state. On the other hand, for the latter samples (x = 0.11 and 0.15), the spectral weight in lower-energy region decreases and the peak-energy in χ^″ (ω) shifts toward high-energy region upon heating. Such different thermal evolution of spin fluctuations between the AF and SC phases is discussed from a viewpoint of degradation of spin correlations by electron-doping which reduces in-plane averaged magnetic interaction.