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We present an electron spin resonance (ESR) study of a single-crystalline spin chain system CuSe2O5 in the frequency range between 9 and 430 GHz. In a wide temperature range above the Nrel temperature TN = 17 K we observe a strong and anisotropic frequency dependence of a resonance linewidth. Although a sizable interchain interaction JIC ≈ 0.1J (J is the intrachain interaction) is present in this system, the ESR results agree well with the Oshikawa-Affleck theory for a one-dimensional S = 1/2 Heisenberg antiferromagnet. This theory is used to extract the anisotropies present in CuSe2O5. We find that the symmetric anisotropic exchange Jc = (0.04 ± 0.01)J and the antisymmetric Dzyaloshinskii-Moriya (DM) interaction D = (0.05 ± 0.01)J are very similar in size in this system. Staggered field susceptibility induced by the presence of the DM interaction is witnessed in the macroscopic susceptibility anisotropy. [ABSTRACT FROM AUTHOR]

Abstract: A combination of highly sensitive torque magnetometry in low magnetic fields and a phenomenological approach to magnetic anisotropy is used to probe the symmetry of the antiferromagnetically ordered state of spin system Cu3TeO6. The results show that the ordered state has four antiferromagnetic domains with spin axis in the directions, in agreement with the previously reported neutron measurements. These results show that this approach, previously applied to ferromagnets and highly anisotropic antiferromagnets, is also successful in determining the symmetry of weakly anisotropic Heisenberg antiferromagnets with multiple spin domains. Possible microscopic origin of magnetic anisotropy is briefly discussed. [Copyright &y& Elsevier]

Employing complementary torque magnetometry and electron spin resonance on single crystals of herbertsmithite, the closest realization to date of a quantum kagome antiferromagnet featuring a spin-liquid ground state, we provide novel insight into different contributions to its magnetism. At low temperatures, two distinct types of defects with different magnetic couplings to the kagome spins are found. Surprisingly, their magnetic response contradicts the threefold symmetry of the ideal kagome lattice, suggesting the presence of a global structural distortion that may be related to the establishment of the spin-liquid ground state. [ABSTRACT FROM AUTHOR]

We present the investigation of a monoclinic compound SeCu0³ using x-ray powder diffraction, magnetization, torque, and electron-spin-resonance. Structurally based analysis suggests that SeCu0³can be considered as a three-dimensional network of tetramers. The values of intratetramer exchange interactions are extracted from the temperature dependence of the susceptibility and amount to ~200 K. The intertetramer coupling leads to the development of long-range antiferromagnetic order at TN= 8 K. An unusual temperature dependence of the effective g tensors is observed, accompanied with a rotation of macroscopic magnetic axes. We explain this unique observation as due to site-selective quantum correlations. [ABSTRACT FROM AUTHOR]