Spin Fluctuations in Itinerant Frustrated Systems
Frustration of magnetic interactions gives rise to various anomalies in the magnetic structure and the critical behavior at the transition temperature. Among them, the ground state of the fully frustrated (FFR) system, which has a macroscopic number of degenerate spin configurations, is attracting much attention. The concept of the quantum spin liquid (QSL) has been proposed as a ground state of FFR. However, no examples has been found so far in ionic crystals. We have studied magnetic and thermal properties of Y(Sc)Mn2where Mn sites form FFR lattice, and found that this compound exhibits really astonishing properties; the very large γ value of 150mJ/Kmol2the enhanced thermal expansion coefficient of 50×10“-6/K etc.
In order to explain these anomalies, we proposed that the ground state of this compound may be in the QSL state, which is characterized by the existence of giant zero point spin fluctuations with antiferromagnetic correlations. Neutron scattering, NMR and µSR experiments have been done to prove this proposal. Effects of impurities, which should be remarkable for the FFR system, were studied by static and dynamical methods. It has been found that the substitution of Al for Mn gives rise to a spin-liquid to spin-glass transition, supporting the FFR characters of Y(Sc)Mn2.
Similar phenomena have been observed in (β-Mn and (β-Mn-Al alloys. It will be shown that Mn II sites in the β-Mn structure can be regarded as three-dimensional twisted Kagome lattice and so as a FFR system.
KeywordsSpin Glass Spin Fluctuation Local Amplitude Antiferromagnetic Correlation Magnetic Neutron
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