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

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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 $T_{\text{sg}} = 23$ 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 $\mathbf{Q}_{m} = (0.46, 0, 0.50)$ and an anisotropy gap of ${\sim}2.5$ meV. Our high $\mathbf{Q}$-resolution data also show that the systems undergo a glassy structural distortion that coincides with the short-range SDW order.
2010-11-15