CPM Seminar

SrCu₂O₃ is a two-leg spin ladder compound having a singlet ground state with a spin gap on the order of 400K. In singlet ground state systems, two or more spins combine to form a spin zero object. A finite amount of energy is needed to break this object into its constituent spins, and so there is a gap in energy between the ground state and first excited state in these materials. In spite of the large energy scale of the spin gap in SrCu₂O₃, the system is extremely sensitive to dilution of the magnetic ladder structure. Our muon spin relaxation measurements (uSR) indicate that substitution of even 1 in 300 spin-1/2 Cu atoms (0.3%) with non-magnetic Zn results in a magnetic ground state. Neutron measurements by Azuma et al. indicate that this magnetic state may, in fact, coexist with a gapped ground state, following a theory proposed by Fukuyama. I will present $\mu$SR data for Zn-doped SrCu₂O₃ in the doping range from 0.0-4.0% Zn. We find a magnetic ground state over the entire range of non-zero Zn concentrations, with a sharp increase in the magnitude of internal magnetic fields near 0.8% Zn, implying a change in the magnetic ground state at this concentration. I will discuss the implications for spin singlet systems

Friday, March 10th 2000, 15:30
Ernest Rutherford Physics Building, room 114