Penetration Depth and Isotope Effect in Highly Overdoped YBCO

Magnetic penetration depth was measured for Y$_{1-x}$Ca$_{x}$Ba$_{2}$Cu$_{3}$O$_{7}$ samples in the range from slightly to highly overdoped carrier concentrations covering Quantum Critical Point (QCP) doping level p=0.2. Together with oxygen isotope exchange experiment in progress, the data should indicate the role of phonons in understanding of the QCP phenomena. Separation of each sample onto different particle size powders along with appropriate model allowed us to extract temperature dependences for in-plane and out-of-plane penetration depth thus defining anisotropy coefficient behavior for the range of highly overdoped compounds.