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Register a new userMagnetic and thermal properties of the S = 1/2 zig-zag spin-chain compound In2VO5
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Static magnetic susceptibility chi, ac susceptibility chi_{ac} and specific heat C versus temperature T measurements on polycrystalline samples of In2VO5 and chi and C versus T measurements on the isostructural, nonmagnetic compound In2TiO5 are reported. A Curie-Wiess fit to the chi(T) data above 175 K for In2VO5 indicates ferromagnetic exchange between V^{4+} (S = 1/2) moments. Below 150 K the chi(T) data deviate from the Curie-Weiss behavior but there is no signature of any long range magnetic order down to 1.8 K. There is a cusp at 2.8 K in the zero field cooled (ZFC) chi(T) data measured in a magnetic field of 100 Oe and the ZFC and field cooled (FC) data show a bifurcation below this temperature. The frequency dependence of the chi_{ac}(T) data indicate that below 3 K the system is in a spin-glass state. The difference Delta C between the heat capacity of In2VO5 and In2TiO5 shows a broad anomaly peaked at 130 K. The entropy upto 300 K is more than what is expected for S = 1/2 moments. The anomaly in Delta C and the extra entropy suggests that there may be a structural change below 130 K in In2VO5.
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We report an investigation on structure and magnetic properties of the $S=3/2$ zigzag spin chain compound BaCoTe$_2$O$_7$. Neutron diffraction measurements reveal BaCoTe$_2$O$_7$ crystallizes in the noncentrosymmetric space group $Ama2$ with a canted $uparrowuparrowdownarrowdownarrow$ spin structure along the quasi-one-dimensional zigzag chain and a moment size of $1.89(2)mu_B$ at 2 K. Magnetic susceptibility and specific heat measurements yield an antiferromagnetic phase transition at $T_N=6.2$ K. A negative Curie-Weiss temperature $Theta_{CW}=-74.7(2)$ K and an empirical frustration parameter of $f=|Theta_text{CW}|/T_text{N}approx12$ is obtained from fitting the magnetic susceptibility, indicating antiferromagnetic interactions and strong magnetic frustration. By employing ultraviolet-visible absorption spectroscopy and first principles calculations, an indirect band gap of 2.68(2) eV is determined. We propose that the canted zigzag spin chain of BaCoTe$_2$O$_7$ may produce a change of the polarization via exchange striction mechanism.
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