Unusual magnetic properties of the low-dimensional quantum magnet Na2V3O7

Abstract

We report the results of low-temperature measurements of the specific heat Cp(T), ac susceptibility chi(T) and 23Na nuclear magnetic resonance NMR of Na2V3O7. At liquid He temperatures Cp(T)/T exhibits broad field-dependent maxima, which shift to higher temperatures upon increasing the applied magnetic field H. Below 1.5 K the ac magnetic susceptibility chi(T) follows a Curie-Weiss law and exhibits a cusp at 0.086 mK which indicates a phase transition at very low temperatures. These results support the previous conjecture that Na2V3O7 is close to a quantum critical point (QCP) at mu_{0}H = 0 T. The entire data set, including results of measurements of the NMR spin-lattice relaxation 1/T1(T), reveals a complex magnetic behavior at low temperatures. We argue that it is due to a distribution of singlet-triplet energy gaps of dimerized V moments. The dimerization process evolves over a rather broad temperature range around and below 100 K. At the lowest temperatures the magnetic properties are dominated by the response of only a minor fraction of the V moments.

arXiv comment10.5 pages, 15 figures. Submitted to Phys. Rev. B

References in corpus (5)

• Three-leg Antiferromagnetic Heisenberg Ladder with Frustrated Boundary Condition; Ground State Properties
• Exchange interactions and magnetic properties of the layered vanadates CaV2O5, MgV2O5, CaV3O7 and CaV4O9
• Soliton binding and low-lying singlets in frustrated odd-legged S=1/2 spin tubes
• Magnetic properties of the coupled ladder system MgV${}_2$O${}_5$
• A low-dimensional spin S = 1/2 system at the quantum critical limit: Na2V2O7

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• Low-lying excitations of the three-leg spin tube using the density-matrix renormalization group method
• Electronic Structure and Exchange Interactions of Na${}_2$V${}_3$O${}_7$
• Cluster mean field study of the Heisenberg model for CuInVO${}_5$
• Formation of collective spins in frustrated clusters
• New structural and magnetic aspects of the nanotube system Na2V3O7
• Breakdown of the conventional spin-wave dynamics and its double-constraint modification in the spin-$\frac{1}{2}$ triangular-prism Heisenberg antiferromagnet