Spin-singlet Quantum Ground State in Zigzag Spin Ladder Cu(CF3 COO)2.

The copper salt of trifluoroacetic acid, Cu(CF3 COO)2 , offers a new platform to investigate the quantum ground states of low-dimensional magnets. In practice, it realizes the ideal case of a solid hosting essentially isolated magnetic monolayers. These entities are constituted by well-separated two-leg half-integer spin ladders organized in a zigzag fashion. The ladders are comprised of dimeric units of edge-sharing tetragonal pyramids coupled through carbon ions. The spin-gap state in this compound was revealed by static and dynamic magnetic measurements. No indications of long range magnetic ordering down to liquid helium temperature were obtained in specific heat measurements. First principles calculations allow estimation of the main exchange interaction parameters, J⊥ =176 K and J∥ =12 K, consistent with the weakly interacting dimers model.