The in-plane penetration depth lambda (T) is measured in electron-doped single crystals Nd1.85Ce0.15CuO4-x (NCCO) and Pr1.85Ce0.15O4-x (PCCO) using an 11 MHz LC resonator. In NCCO, lambda (T) exhibits a minimum at 3.8 K and a pronounced upturn down to 0.4 K due to the paramagnetic contribution of Nd3+ ions. The London penetration depth contribution is linear in T. The paramagnetic contribution is absent in PCCO, where lambda (T)similar toT(2) at low temperatures. Our results indicate the presence of nodes in the superconducting gap, i.e., non s-wave symmetry of the order parameter in electron-doped cuprates. [References: 9]
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