Neutron scattering evidence for isolated spin-12ladders in(C5D12N)2CuBr4

Abstract

Inelastic neutron scattering was used to determine the spin Hamiltonian for the singlet ground-state system of fully deuterated BPCB, ${({\text{C}}_{5}{\text{D}}_{12}\text{N})}_{2}{\text{CuBr}}_{4}$. A two-leg spin-1/2 ladder model, with ${J}_{\ensuremath{\perp}}=(1.09\ifmmode\pm\else\textpm\fi{}0.01)\text{ }\text{meV}$ and ${J}_{\ensuremath{\parallel}}=(0.296\ifmmode\pm\else\textpm\fi{}0.005)\text{ }\text{meV}$, accurately describes the data. The experimental limit on the effective interladder exchange constant is $|{J}_{\text{int}}^{\text{eff}}|\ensuremath{\lesssim}0.006\text{ }\text{meV}$, and the limit on total diagonal, intraladder exchange is $|{J}_{F}+{J}_{{F}^{\ensuremath{'}}}|\ensuremath{\le}0.1\text{ }\text{meV}$. Including the effects of copper to bromide covalent spin transfer on the magnetic form factor, the experimental ratios of intraladder bond energies are consistent with the predictions of continuous unitary transformation.