Doping effects in a S = 1/2 spin ladder system near quantum criticality

Spin ladders are excellent model systems for studying quantum phase transitions, as they exhibit a quantum critical point between non-magnetic spin singlet dimers to Néel magnetic order as inter-ladder exchange is increased. Ba2CuTeO6 is a Cu2+ S = 1/2 two-leg spin ladder system, that is close to the quantum critical point on the Néel ordered side. We have prepared the solid solution Ba2CuTe1-xWxO6 in an attempt to tune magnetic interactions past the quantum critical point. We will use muon spin rotation and relaxation to investigate the ground state of these materials. This will allow us to determine whether we have tuned the system to quantum criticality, or whether the materials remain magnetically ordered.