Frustrated Cuprate Route from Antiferromagnetic to Ferromagnetic Spin-12 Heisenberg Chains: Li2ZrCuO4 as a Missing Link near the Quantum Critical Point

S.-L. Drechsler; O. Volkova; A. N. Vasiliev; N. Tristan; J. Richter; M. Schmitt; H. Rosner; J. Málek; R. Klingeler; A. A. Zvyagin; B. Büchner

doi:10.1103/PhysRevLett.98.077202

Frustrated Cuprate Route from Antiferromagnetic to Ferromagnetic Spin-12 Heisenberg Chains: Li2ZrCuO4 as a Missing Link near the Quantum Critical Point

S.-L. Drechsler, O. Volkova, A. N. Vasiliev, N. Tristan, J. Richter, M. Schmitt, H. Rosner, J. Málek, R. Klingeler, A. A. Zvyagin, B. Büchner

DOI 10.1103/PhysRevLett.98.077202 · Physical Review Letters

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Abstract

From thermodynamics, local spin density approximation+Hubbard U studies and exact diagonalizations of a five-band Hubbard model on CuO2 stripes we find that Li2ZrCuO4 (Li2CuZrO4 in traditional notation) is close to a ferromagnetic critical point. Analyzing its susceptibility χ(T) and specific heat cp(T,H) within a Heisenberg model, we show that the ratio of the 2nd to the 1st neighbor exchange integrals α=−J2/J1∼0.3 is close to the critical value αc=14. Comparing with related chain cuprates we explain the rather strong field dependence of cp, the monotonic downshift of the peak of χ(T), and its increase for α→αc+0.