期刊
PHYSICAL REVIEW B
卷 80, 期 18, 页码 -出版社
AMER PHYSICAL SOC
DOI: 10.1103/PhysRevB.80.180418
关键词
Heisenberg model; Ising model; magnetic susceptibility; magnetic transitions; short-range order; spin dynamics; spin waves; superconducting materials; superconducting transitions
We study finite temperature properties of a generic spin-orbital model relevant to transition metal compounds, having coupled quantum Heisenberg-spin and Ising-orbital degrees of freedom. The model system undergoes a phase transition, consistent with that of a two-dimensional Ising model, to an orbitally ordered state at a temperature set by short-range magnetic order. At low temperatures the orbital degrees of freedom freeze out and the model maps onto a quantum Heisenberg model. The onset of orbital excitations causes a rapid scrambling of the spin spectral weight away from coherent spin waves, which leads to a sharp increase in uniform magnetic susceptibility just below the phase transition, reminiscent of the observed behavior in the Fe-pnictide materials.
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