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Information × Registration Number 0224U032976, (0124U003979) , R & D reports Title Frustrated quantum magnets under various external conditions popup.stage_title Спін-S Гайзенберговий антиферомагнетик на гратці кагоме. Head Derzhko Oleh V., Доктор фізико-математичних наук Registration Date 13-12-2024 Organization Institute of Condensed Matter Physics of the National Academy of Sciences of Ukraine popup.description1 There are several goals outlined in the proposal: To apply recently developed theoretical approaches for explaining the low-temperature measurements for magnetically frustrated compounds; to resolve long-standing quests for low-temperature thermodynamics of several frustrated quantum Heisenberg antiferromagnets; to explore the thermodynamics of the S=1/2 Shastry-Sutherland Heisenberg spin system in a wide range of model parameters and apply theoretical predictions for interpreting experiments. popup.description2 Quantum spin-lattice systems for which the interspin interactions cannot be satisfied simultaneously (frustration) are known to be hard for theoretical studies, since the direct methods of statistical mechanics are often inapplicable. We use high-temperature expansion series up to order 11 in the inverse temperature and the entropy method to calculate the magnetic specific heat and the magnetic uniform susceptibility for the kagome-lattice Heisenberg antiferromagnet with spin S > 1/2. We complement these calculations by exact diagonalization and finite-temperature Lanczos method data for finite systems. We discuss how the temperature dependence of the specific heat varies as the spin quantum number S grows. The hyperkagome-lattice S = 1/2 Heisenberg ferromagnet is studied by means of (i) the linear spin-wave theory, (ii) the double-time temperature Green’s functions, (iii) high-temperature expansions, and (iv) quantum Monte Carlo simulations to examine the effect of lattice geometry on the finite-temperature properties. We have found that the Curie temperature Tc for the hyperkagome-lattice (frustrated lattice) ferromagnet is about 0.33|J| that is smaller than Tc for the diamond-lattice (another three-dimensional lattice with the same coordination number 4 but bipartite one) ferromagnet by about 25%. Product Description popup.authors Verkholyak Taras M. Hutak Taras I. Krokhmalskyi Taras Y. Parymuda Maksym R. popup.nrat_date 2024-12-13 Close