Berlin 2012 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 49: Correlated Electrons: Low-dimensional Systems - Materials 4

TT 49.5: Talk

Friday, March 30, 2012, 10:30–10:45, H 3005

Field-induced staggered moment stabilization in frustrated quantum magnets — •Burkhard Schmidt, Mohammad Siahatgar, and Peter Thalmeier — Max-Planck-Institut für Chemische Physik fester Stoffe, Dresden

For low-dimensional frustrated quantum magnets, the dependence of the staggered moment on an applied magnetic field is nonmonotonic: For small and intermediate fields, quantum fluctuations are gradually suppressed, leading to an increase of the staggered moment as a function of the field strength. For large applied magnetic fields, the classically expected field dependence is recovered, namely a monotonous decrease with increasing field strength. The staggered moment is eventually suppressed when reaching the fully polarized state at the saturation field. The quantitative analysis of this behavior is an excellent tool to determine the frustration parameter of a given compound. We apply linear spin-wave theory, numerical exact diagonalization, and a self-consistent RPA theory. As an example, we discuss the recently measured field dependence of the magnetic neutron scattering intensity of Cu(pz)₂(ClO₄)₂ in the framework of the S=1/2 two-dimensional (2D) J₁-J₂ Heisenberg model. Our results show that Cu(pz)₂(ClO₄)₂ is a quasi-2D antiferromagnet with intermediate frustration J₂/J₁=0.2. With this ratio, the observed reentrant behavior of the magnetic ordering temperature as a function of the applied magnetic field can be understood as a consequence of the reduced quantum fluctuations as well.