Speaker
Description
Cu(tn)Cl$_2$ (tn = 1,3-diaminopropane) has been previously identified as a potential realization of a quasi-two-dimensional, spatially anisotropic triangular Heisenberg antiferromagnet with spin $1/2$, intralayer exchange coupling, $J/k_B \approx -3$ K, and interlayer exchange coupling, $J^{\prime} \approx 0.001\,J$. These studies indicated a field-induced anomaly forming below $1$ K in magnetic fields up to $7$ T and this anomaly was assigned to a Berezinskii-Kosterlitz-Thouless phase transition [1]. First-principle calculations point to the quasi-two-dimensional character of the exchange paths, while in the first approximation the system could be identified as a quasi-two-dimensional $S = 1/2$ Heisenberg antiferromagnet on the rectangular lattice with the intrachain coupling $J_1/k_B \approx$ $4.3$ K and the interaction ratio $R = J_2/J_1\approx$ $0.46$ [2].
In this work, we focused on the experimental study of magnetostructure correlations in Cu(tn)(SCN)$_2$ system with spin $S = 1/2$. Cu(tn)(SCN)$_2$ shows a similar chemical structure compared to Cu(tn)Cl$_2$ with the same system of hydrogen bonds [3]. Specific heat measurements of powder sample were performed in a commercial Physical Property Measurement System (PPMS) in the temperature range from $0.4$ K to $20$ K in magnetic fields up to $9$ T. The temperature dependence of susceptibility was measured in a commercial Quantum Design SQUID Magnetometer (MPMS) in the temperature range from $1.8$ to $300$ K in the magnetic field $100$ mT. The specific heat studies in zero magnetic field did not indicate a phase transition to long-range magnetic order down to $0.4$ K. The study of the susceptibility and magnetization of the Cu(tn)(SCN)$_2$ powder sample showed that the investigated system is characterized by an antiferromagnetic exchange interaction, which is approximately $10$ times smaller compared to the Cu(tn)Cl$_2$ system. The weakening of exchange interactions could be attributed to the presence of the isothiocyanato ligands.
Acknowledgements
The financial support of projects VEGA 1/0132/22, APVV-18-0197 and APVV-22-0172 is acknowledged.
References
[1] A. Orendáčová et al, “Interplay of frustration and magnetic field in the two-dimensional quantum antiferromagnet Cu($tn$)Cl$_2$,“ Physical Review B, vol. 80, no. 14. American Physical Society (APS), Oct. 21, 2009. https://doi.org/10.1103/physrevb.80.144418
[2] R. Tarasenko et al, “Extraordinary two-dimensionality in the $S=$ 1/2 spatially anisotropic triangular quantum magnet Cu(1,3-diaminopropane)Cl$_2$ with modulated structure,” Physical Review B, vol. 108, no. 21. American Physical Society (APS), Dec. 28, 2023. https://doi.org/10.1103/physrevb.108.214432
[3] A. O. Legendre et al., “A 2D coordination polymer with brick-wall network topology based on the [Cu(NCS)2(pn)] monomer,” Inorganic Chemistry Communications, vol. 10, no. 7. Elsevier BV, pp. 815–820, Jul. 2007. https://doi.org/10.1016/j.inoche.2007.04.005
