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Abstract

For low-dimensional frustrated quantum magnets, the dependence of the staggered moment on a 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 magnetic compound. We have developed a general finite-size scaling scheme for numerical exact-diagonalization data of low-dimensional frustrated magnets, which we apply to 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) J (1)-J (2) Heisenberg model. We also apply linear spin-wave theory to complement our numerical findings. Our results show that Cu(pz)(2)(ClO4)(2) is a quasi-2D antiferromagnet with intermediate frustration J (2)/J (1) = 0.2.