Investigation of the Spin-Glass Regime between the Antiferromagnetic and Superconducting Phases in Fe1+ySexTe1-x

Using bulk magnetization along with elastic and inelastic neutron scattering techniques, we have investigated the phase diagram of Fe1+ySexTe1-x and the nature of magnetic correlations in three nonsuperconducting samples of Fe1.01Se0.1Te0.9, Fe1.01Se0.15Te0.85, and Fe1.02Se0.3Te0.7. 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 similar to 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.