Structure and magnetism in the metal organic quantum magnet Cu-CPA

Quantum spin ladders bridge the gap between one and two dimensions and have complex excitation spectra, which depend on the relative strengths of the leg and rung exchange interactions. While the realization of strong-rung ladders is fairly common, strong-leg ladders are a much rarer occurrence. In this contribution, we study an organometallic one-dimensional magnet (CPA)₂CuBr₄, (Cu-CPA) first reported in [1] and proposed to realize the strong-leg spin ladder model.



Through detailed bulk measurements and scattering experiments, we have discovered previously unknown structural phase transitions that take place below 200 K. The low-temperature structure that gives rise to the magnetic properties is described as a double spin ladder [2]. We will report the detailed structure of the ladder and discuss the implications of this structure on the magnetic properties. Finally, we will discuss our ongoing detailed investigations of the low-temperature magnetism.





[1] R.D. Willett et. al., Inorg. Chem. 43, 3804 (2004)

[2] J. Philippe et. al., Phys. Rev. B 110, 094101 (2024)