arXiv subjects

Tomoyuki Koga

Publications and source records attributed to Tomoyuki Koga.

2 recordsLinked to original sources

arXiv2016

Magnetic Structure of the $S\,{=}\,1/2$ Quasi-Two-Dimensional Square-Lattice Heisenberg Antiferromagnet Sr$_2$CuTeO$_6$

The magnetic structure of the double perovskite compound Sr$_2$CuTeO$_6$ was determined from neutron powder diffraction data. This material is magnetically described as an $S\,{=}\,1/2$ quasi-two-dimensional square-lattice Heisenberg model with antiferromagnetic nearest-neighbor and next-nearest-neighbor interactions. Sr$_2$CuTeO$_6$ undergoes a magnetic phase transition at $T_{\rm N}\,{\simeq}\,29\,$ K. The spin structure below $T_{\rm N}$ is Néel antiferromagnetic on the square lattice, which means that the nearest-neighbor interaction ($J_1$) is stronger than the next-nearest-neighbor interaction ($J_2$), in contrast to other isostructural compounds such as Ba$_2$CuWO$_6$ and Sr$_2$CuWO$_6$, for which $|J_1|\,{<}\,|J_2|$ is realized.

cond-mat.str-el↗

arXiv2014

Strong Suppression of Magnetic Ordering in an S = 1/2 Square-Lattice Heisenberg Antiferromagnet Sr2CuTeO6

We report the magnetic susceptibility and the low-temperature specific heat of a double perovskite compound, Sr2CuTeO6, which is expected as the spin-1/2 square-lattice Heisenberg antiferromagnet with nearest-neighbor J1 and next-nearest-neighbor J2 exchange interactions. The specific heat exhibits a sharp lambda-like anomaly at TN = 4.8 K indicative of magnetic ordering, which is much lower than those in isostructural A2CuMO6 with A = Ba, Sr and M = W, Mo. This indicates the strong suppression of magnetic ordering in Sr2CuTeO6. We estimate the exchange constant J1/kB ~ 80 K and J2/J1 < 0.07 from magnetic susceptibility data using Pade approximation of high temperature expansion and quantum Monte Carlo method. The strong suppression of magnetic ordering in Sr2CuTeO6 should be ascribed to the weekness of the interlayer exchange.

cond-mat.str-el↗