Measurements of magnetic susceptibility, heat capacity and thermal expansion are reported for single crystalline CuSb$_{2}$O$_{6}$ in the temperature range $5<T<350$ K. The magnetic susceptibility exhibits a broad peak centered near 60 K that is typi
cal of one-dimensional antiferromagnetic compounds. Long-range antiferromagnetic order at $T_N$ = 8.7 K is accompanied by an energy gap ($Delta$ = 17.48(6) K). This transition represents a crossover from one- to three-dimensional antiferromagnetic behavior. Both heat capacity and the thermal expansion coefficients exhibit distinct jumps at $T_N$, which are similar to those observed at the normal-superconducting phase transition in a superconductor. This behavior is quite unusual, and is presumably associated with a Spin-Peierls transition occurring as a result of three-dimensional phonons coupling with {it Jordan-Wigner-transformed} Fermions.
The structure, morphology, and electrical properties of epitaxial a-axis oriented thin films of Nd(0.2)Sr(0.8)MnO(3) are reported for thicknesses 10 nm <= t <= 150 nm. Films were grown with both tensile and compressive strain on various substrates. I
t is found that the elongated crystallographic c-axes of the films remain fully strained to the substrates for all thicknesses in both strain states. Relaxation of the a and b axes is observed for t>= 65 nm with films grown under tensile strain developing uniaxial crack arrays (running along the c axis) due to a highly anisotropic thermal expansion. For the latter films, the room-temperature in-plane electrical resistivity anisotropy, rho_b/rho_c, increases approximately exponentially with increasing film thickness to values of ~1000 in the thickest films studied. Films under tension have their Neel temperatures enhanced by ~25 K independent of thickness, consistent with an enhancement of ferromagnetic exchange along their expanded c axes.
The application of weak electric fields (<~ 100 V/cm) is found to dramatically enhance the lattice thermal conductivity of the antiferromagnetic (AF) insulator CaMnO(3) over a broad range of temperature about the Neel ordering point (125 K). The effe
ct is coincident with field-induced de-trapping of bound electrons, suggesting that phonon scattering associated with short- and long-ranged AF order is suppressed in the presence of the mobilized charge. This interplay between bound charge and spin-phonon coupling might allow for the reversible control of spin fluctuations using weak external fields.
