Investigation of the Spin-Glass Regime between the Antiferromagnetic and Superconducting Phases in Fe_1+ySe_xTe_1-x

Using bulk magnetization along with elastic and inelastic neutron scattering techniques, we have investigated the phase diagram of Fe _1+ySe_xTe_1-x and the nature of magnetic correlations in three nonsuperconducting samples of Fe_1.01Se _0.1Te_0.9, Fe_1.01Se_0.15Te _0.85, and Fe_1.02Se_0.3Te_0.7. A cusp and hysteresis in the temperature dependence of the magnetization for the x = 0:15 and 0.3 samples indicates spin-glass (SG) ordering below T_sg = 23 K. Neutron scattering measurements indicate that the spin-glass behavior is associated with short-range spin density wave (SDW) ordering characterized by a static component and a low-energy dynamic component with a characteristic incommensurate wave vector of Q_m = (0.46, 0, 0.50) and an anisotropy gap of ̃2:5 meV. Our high Q-resolution data also show that the systems undergo a glassy structural distortion that coincides with the short-range SDW order.