期刊
PHYSICAL REVIEW B
卷 79, 期 5, 页码 -出版社
AMER PHYSICAL SOC
DOI: 10.1103/PhysRevB.79.054526
关键词
antiferromagnetic materials; arsenic alloys; band model of magnetism; barium alloys; energy gap; iron alloys; magnetic anisotropy; spin fluctuations
Neutron scattering measurements were performed to investigate magnetic excitations in a single-crystal sample of the ternary iron arsenide BaFe2As2, a parent compound of a recently discovered family of Fe-based superconductors. In the ordered state, we observe low energy spin-wave excitations with a gap energy Delta=9.8(4) meV. The in-plane spin-wave velocity v(ab) and out-of-plane spin-wave velocity v(c) measured at 12 meV are 280(150) and 57(7) meV A, respectively. At high energy, we observe anisotropic scattering centered at the antiferromagnetic wave vectors. This scattering indicates two-dimensional spin dynamics, which possibly exist inside the Stoner continuum. At T-N=136(1) K, the gap closes and quasielastic scattering is observed above T-N, indicative of short-range spin fluctuations. In the paramagnetic state, the scattering intensity along the L direction becomes rodlike, characteristic of uncorrelated out-of-plane spins, attesting to the two-dimensionality of the system.
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