We report on pulsed-field magnetization studies of the quasi-two-dimensional spin system Cu(pyz)2(HF2)PF6. The magnetization saturates at BCab=37.5BCab=375 T and BCc=33.8BcC=338 T for in-plane and ...out-of-plane orientations of the applied magnetic field, respectively. In addition, the angular dependence of the g-factor studied by electron-spin resonance reveals orbital overlap in the ab plane suggesting a quasi-two-dimensional square-lattice network of Cu spins. It is argued that the high-field behavior is governed by the two-dimensional nature of the spin correlations due to the large anisotropy of the exchange couplings.
We report on pulsed-field magnetization studies of the quasi-two-dimensional spin system Cu(pyz)
2
(HF
2
)PF
6
. The magnetization saturates at
T and
T for in-plane and out-of-plane orientations of ...the applied magnetic field, respectively. In addition, the angular dependence of the
g
-factor studied by electron-spin resonance reveals orbital overlap in the
ab
plane suggesting a quasi-two-dimensional square-lattice network of Cu spins. It is argued that the high-field behavior is governed by the two-dimensional nature of the spin correlations due to the large anisotropy of the exchange couplings.
Low-energy magnetic excitations in the spin-1/2 chain compound (C\(_6\)H\(_9\)N\(_2\))CuCl\(_3\) known as (6MAP)CuCl\(_3\) are probed by means of tunable-frequency electron spin resonance. Two modes ...with asymmetric (with respect to the \(h\nu=g\mu_B B\) line) frequency-field dependences are resolved, illuminating the striking incompatibility with a simple uniform \(S=\frac{1}{2}\) Heisenberg chain model. The unusual ESR spectrum is explained in terms of the recently developed theory for spin-1/2 chains, suggesting the important role of next-nearest-neighbor interactions in this compound. Our conclusion is supported by model calculations for the magnetic susceptibility of (6MAP)CuCl\(_3\), revealing a good qualitative agreement with experiment.
BaCuSi2O6 can be regarded as an almost ideal realization of an system of weakly interacting spin dimers with spin-singlet ground state and gapped excitation spectrum. We argue that the fine structure ...observed in low-temperature EPR spectra of BaCuSi2O6 is a fingerprint of triplet excitations (excitons). Analyzing the angular dependence of the exciton modes allows us to precisely calculate the zero-field splitting within the triplet states and, correspondingly, the anisotropy parameter, . The proposed procedure can be applied for studying anisotropy effects in a large number of gapped quantum antiferromagnets with dimerized or alternating spin structure.
Spin-1/2 Heisenberg antiferromagnets Cs\(_2\)CuCl\(_4\) and Cs\(_2\)CuBr\(_4\) with distorted triangular-lattice structures are studied by means of electron spin resonance spectroscopy in magnetic ...fields up to the saturation field and above. In the magnetically saturated phase, quantum fluctuations are fully suppressed, and the spin dynamics is defined by ordinary magnons. This allows us to accurately describe the magnetic excitation spectra in both materials and, using the harmonic spin-wave theory, to determine their exchange parameters. The viability of the proposed method was proven by applying it to Cs\(_2\)CuCl\(_4\), yielding \(J/k_B=4.7(2)\) K, \(J'/k_B=1.42(7)\) K \(J'/J\simeq 0.30\) and revealing good agreement with inelastic neutron-scattering results. For the isostructural Cs\(_2\)CuBr\(_4\), we obtain \(J/k_B=14.9(7)\) K, \(J'/k_B=6.1(3)\) K, \(J'/J\simeq 0.41\), providing exact and conclusive information on the exchange couplings in this frustrated spin system.
By means of electron spin resonance investigations we revealed the crucial role of the interchain coupling in the spin dynamics of the spin-1/2 Heisenberg antiferromagnetic (AF) chain material ...copper-pyrazine-dinitrate, Cu(C\(_4\)H\(_4\)N\(_2\))(NO\(_3\))\(_2\). We found that the dominating interchain interaction is of a zig-zag type. This interaction gives rise to geometrical frustration effects and strongly influences the character of AF ordering. Combining our experimental findings with the results of a quasiclassical approach we argue that at low temperatures the system orders in an incommensurate spiral state.
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