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Theoretical Study of Spin Resonance in Triangular Lattice Heisenberg Antiferromagnet with Easy Axis for Anisotropy Perpendicular to the Plane

1987; Physical Society of Japan; Volume: 56; Issue: 4 Linguagem: Inglês

10.1143/jpsj.56.1577

1347-4073

Toshihiko Suzuki, Yuhei Natsume,

Magnetic and transport properties of perovskites and related materials

The spin wave theory is developed on the basis of a triangular lattice Heisenberg antiferromagnet with a single-ion type anisotropy whose easy axis is perpendicular to the lattice plane ( c -plane) in order to investigate the low-lying excited states of Néel-like 120° structure on a a - c plane. As a result of calculation only for electronic spins S as to k =0, a characteristic mode with quite a low energy is obtained. This mode corresponds to the swinging motion in the a - c plane, and reflects the present characteristic anisotropy and a frustration effect. In addition, the behavior of this mode under the influence of hyperfine coupling (- A S · I ) with nuclear spins I is discussed. Consequently, the possibility of the abnormal NMR line whose energy is far less than that of normal NMR ( A S ) is pointed out. Further, the dispersion relation for various modes is discussed.