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arXiv 1303.5271cond-mat.str-el
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S=1/2三角格子Heisenberg反铁磁体Ba3CoSb2O9的磁化过程和集体激发

Magnetization Process and Collective Excitations in the S=1/2 Triangular-Lattice Heisenberg Antiferromagnet Ba3CoSb2O9

Takuya Susuki, Nobuyuki Kurita, Takuya Tanaka, Hiroyuki Nojiri, Akira Matsuo, Koichi Kindo, Hidekazu Tanaka

摘要:

我们对具有代表性的二维自旋1/2海森堡反铁磁体Ba $_3$ CoSb $_2$ O $_9$单晶进行了高场磁化强度和ESR测量,并确定了所有的磁性参数。对于平行于$ab$平面的外加磁场$H$,整个磁化曲线(包括饱和磁化强度三分之一处的平台($M_\mathrm{s}$))与理论计算的结果非常一致,除了$(3/5)M_\mathrm{s}$附近的异常,指示额外的场诱导转变。然而,对于$H\,{\parallel}\,c$,磁化曲线在$M_\mathrm{s}/3$附近呈现尖点。高于Néel温度的顺磁共振信号表明几乎各向同性的$g$ -因子。在有序状态下观察到的集体ESR模式的详细分析,结合磁化过程,提供了弱易面各向异性的证据。

英文摘要:

We have performed high-field magnetization and ESR measurements on Ba$_3$CoSb$_2$O$_9$ single crystals, as a representative two-dimensional spin-1/2 Heisenberg antiferromagnet on a uniform triangular lattice, and have determined all the magnetic parameters. For an applied magnetic field $H$ parallel to the $ab$-plane, the entire magnetization curve including the plateau at one-third of the saturation magnetization ($M_\mathrm{s}$) is in excellent agreement with the results of theoretical calculations except an anomaly near $(3/5)M_\mathrm{s}$, indicative of an additional field-induced transition. However, for $H\,{\parallel}\,c$, the magnetization curve exhibits a cusp near $M_\mathrm{s}/3$. Paramagnetic resonance signals above the Néel temperature indicate the nearly isotropic $g$-factor. A detailed analysis of the collective ESR modes observed in the ordered state, combined with the magnetization process, provides evidence of the weak easy-plane anisotropy.

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