Frustrated cuprate route from antiferromagnetic to ferromagnetic spin-1/2 Heisenberg chains: Li2ZrCuO4 as a missing link near the quantum critical point.
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 chi(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 alpha=-J2/J1 approximately 0.3 is close to the critical value alphac=1/4. Comparing with related chain cuprates we explain the rather strong field dependence of cp, the monotonic downshift of the peak of chi(T), and its increase for alpha-->alphac+0.
Drechsler
S-L
SL
Leibniz-Institut für Festkörper-und Werkstoffforschung (IFW) Dresden, P.O. Box 270116, D-01171 Dresden, Germany. s.l.drechsler@ifw-dresden.de
Volkova
O
O
Vasiliev
A N
AN
Tristan
N
N
Richter
J
J
Schmitt
M
M
Rosner
H
H
Málek
J
J
Klingeler
R
R
Zvyagin
A A
AA
Büchner
B
B