The tunable quantum spin ladder Cu(Qnx)(Cl${}_{(1-x)}$Br${}_x$)${}_2$

Abstract

We report magnetic, specific heat and ESR measurements on a series of $S=1/2$ spin ladder compounds Cu(Qnx)(Cl${}_{(1-x)}$Br${}_x$)${}_2$. Down to $T=2$ K all the observables can be described by the spin ladder model with about 1% of $S=1/2$ impurities in the background, which are present even in a nominally pure Cu(Qnx)Cl${}_2$ and Cu(Qnx)Br${}_2$, for the whole range of $0\le x\le 1$. We extract ladder exchange constants $J_l(x)$ and $J_r(x)$ as well as the gap value $\Delta (x)$ by comparing the experimental data to quantum Monte-Carlo simulations. As the ESR measurements show the $g$-factor of impurities to be precisely equal to $g$-factor of the ladder spins, we suppose the impurities to be the consequence of structural defects resulting in a broken ladder ends.

8 pages, 7 figures

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Cited by in corpus (5)

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• Magnetic phase diagram of a spin S=1/2 antiferromagnetic two-leg ladder in the presence of modulated along legs Dzyaloshinskii-Moriya interaction
• Chemical composition induced quantum phase transition in Cs${}_{1-x}$Rb${}_x$FeCl${}_3$
• Electron Spin Resonance in a Spin-1/2 Heisenberg Strong-rung Ladder
• Raman study of spin excitations in the tunable quantum spin ladder Cu(Qnx)(Cl${}_{1-x}$Br${}_x$)${}_2$