One-dimensional magnets are very interesting, although it is well-known that there is no long range-order[1]. Because a spin chain, which is defined as a one-dimensional line of spins pointing in particular directions, in one-dimensional magnets has the possibility of complex excitations like spinons which have spin-1/2 in chains with S=1/2. Lately, we have reported a quasi-one-dimensional S=1 chain system NiTe2O5[2]. About the crystallographic structural feature of NiTe2O5, NiO6 octahedra are connected to each other through the edge-sharing and the spin(S=1) of each Ni2+ ion at the center of the octahedra forms a quasi-one-dimensional spin chain. By decreasing temperature, spins of Ni2+ ions are ordered as antiferromagnetic long-range order at 30.5 K. The single crystal neutron diffraction reveals the unconventional critical behavior of the order parameter around the ordering temperature. 125Te nuclear magnetic resonance(NMR) experiments exhibit intriguing persistent spin fluctuation above the ordering temperature[3]. More recently, even magnetoelectric(ME) coupling was reported[4]. Thermal transport has been used to an experimental tool in solid-state physics even when dealing with magnetic systems[5]. Because heat transport via the spin system itself and thermal conductivities are influenced by scattering between phonon and magnetic excitations. By using the thermal transport experiments on NiTe2O5 single crystal, we studied thermodynamic properties associated with these unusual magnetic behaviors in NiTe2O5.
[1] Stephen Blundell, Magnetism in Condensed Matter, Oxford ; New York : Oxford University Press (2001). [2] Jun Han Lee, Marie Kratochvílová, Huibo Cao, Zahra Yamani, JS Kim, Je-Geun Park, GR Stewart, Yoon Seok Oh, Unconventional critical behavior in the quasi-one-dimensional S=1 chain NiTe2O5, Physical Review B 100, 144441 (2019). [3] Seung-Ho Baek, Jun Han Lee, Yoon Seok Oh, Kwang-Yong Choi, Bernd Büchner, Persistence of Ising-like easy-axis spin correlations in the paramagnetic state of the spin-1 chain compound NiTe2O5, Physical Review B 104, 214431 (2021). [4] Ajay Tiwari, D. Chandrasekhar Kakarla, G. Macam, C. H. Hsu, F. C. Chuang, H. C. Wu, T. W. Kuo, Arkadeb Pal, H. Chou, D. P. Gulo, H.L. Liu, Y. C. Lai, C. A. Lee, Mitch M. C. Chou, H. D. Yang, Spin-lattice-charge coupling in quasi-one-dimensional spin-chain NiTe2O5, Physical Review Materials 6, 044409 (2022). [5] A. V. Sologubenko, T. Lorenz, H. R. Ott, A. Freimuth, Thermal conductivity via magnetic excitations in spin-chain materials, J. Low Temp. Phys. 147, 387-403 (2007).