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  1. Free, publicly-accessible full text available May 1, 2024
  2. Low-temperature thermal conductivity ( κ ), as well as the magnetic properties and specific heat, are studied for the frustrated zigzag spin-chain material SrEr 2 O 4 by using single-crystal samples. The specific heat data indicate the long-range antiferromagnetic transition at ∼ 0.73 K and the existence of strong magnetic fluctuations. The magnetizations at very low temperatures for magnetic field along the c axis (spin chain direction) or the a axis reveal the field-induced magnetic transitions. The κ shows a strong dependence on magnetic field, applied along the c axis or the a axis, which is closely related to the magnetic transitions. Furthermore, high magnetic field induces a strong increase of κ . These results indicate that thermal conductivity along either the c axis or the a axis are mainly contributed by phonons, while magnetic excitations play a role of scattering phonons. 
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  3. Abstract

    The single-ion anisotropy and magnetic interactions in spin-ice systems give rise to unusual non-collinear spin textures, such as Pauling states and magnetic monopoles. The effective spin correlation strength (Jeff) determines the relative energies of the different spin-ice states. With this work, we display the capability of capacitive torque magnetometry in characterizing the magneto-chemical potential associated with monopole formation. We build a magnetic phase diagram of Ho2Ti2O7, and show that the magneto-chemical potential depends on the spin sublattice (αorβ), i.e., the Pauling state, involved in the transition. Monte Carlo simulations using the dipolar-spin-ice Hamiltonian support our findings of a sublattice-dependent magneto-chemical potential, but the model underestimates theJefffor theβ-sublattice. Additional simulations, including next-nearest neighbor interactions (J2), show that long-range exchange terms in the Hamiltonian are needed to describe the measurements. This demonstrates that torque magnetometry provides a sensitive test forJeffand the spin-spin interactions that contribute to it.

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  4. We have performed combined elastic neutron diffuse, electrical transport, specific heat, and thermal conductivity measurements on the quasi–one-dimensional Ba 3 Co 2 O 6 (CO 3 ) 0.7 single crystal to characterize its transport properties. A modulated superstructure of polyatomic CO 3 2− is formed, which not only interferes the electronic properties of this compound, but also reduces the thermal conductivity along the c-axis. Furthermore, a large magnetic entropy is observed to be contributed to the heat conduction. Our investigations reveal the influence of both structural and magnetic effects on its transport properties and suggest a theoretical improvement on the thermoelectric materials by building up superlattice with conducting ionic group. 
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