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arXiv 0908.2842cond-mat.str-elcond-mat.other
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耦合双自旋梯BiCu2PO6中的掺杂效应

Doping effects in the coupled, two-leg spin ladder BiCu2PO6

B. Koteswararao, A. V. Mahajan, L. K. Alexander, J. Bobroff

摘要:

本文报道了BiCu_2PO_6双自旋梯系统的制备、X射线衍射、磁化率chi(T)和热容Cp(T)测量结果,以及Cu位Zn掺杂(S = 0)、Cu位Ni掺杂(S = 1)和Bi位Ca掺杂(空穴)的样品。而Zn显示完全固溶,Ni可以掺杂到约20%,Ca可以掺杂到约15%。未掺杂化合物的磁化强度和热容量数据表明存在阻挫效应。在所有样品中,低温下的chi(T)随着掺杂含量的增加而增加。Zn诱导的磁化率小于由于有效S=1/2的时刻,可能是由于沿着腿挫败次近邻相互作用。当Zn含量x > 0.01时,chi(T)在低温下偏离居里定律。Zn掺杂样品的磁比热数据Cm(T)在低温下表现出弱异常,与chi(T)行为一致。这些异常现象表明在低温下自旋冻结。相比之下,在Ni掺杂的样品上观察到chi(T)和Cm(T)的显著影响。与Zn掺杂样品不同,零场冷却(ZFC)和场冷却(FC)chi(T)数据在低温下彼此不同,清楚地指示向自旋玻璃状相的转变。在Ca或Pb掺杂的样品中没有发现异常。

英文摘要:

We report preparation, x-ray diffraction, magnetic susceptibility chi(T) and heat capacity Cp(T) measurements on the undoped samples as also samples with Zn-doped (S = 0) at Cu site, Ni doped (S = 1) at Cu site, and Ca-doped (holes) at Bi site in the coupled two-leg spin ladder system BiCu2PO6. While, Zn shows complete solid solubility, Ni could be doped to about 20% and Ca to about 15%. Magnetization and heat capacity data in the undoped compound point towards the existence of frustration effects. In all the samples, the chi(T) at low temperature increases with doping content. The Zn-induced susceptibility is smaller than that due to effective S=1/2 moments possibly due to frustrating next-nearest-neighbor interactions along the leg. For Zn content x > 0.01, chi(T) deviates from the Curie-law at low temperatures. The magnetic specific heat data Cm(T) for the Zn-doped samples show weak anomalies at low temperature in agreement with chi(T) behavior. The anomalies are suggestive of spin freezing at low-T. In contrast, prominent effects are observed in chi(T) and Cm(T) on Ni-doped samples. The zero-field-cooled (ZFC) and field-cooled (FC) chi(T) data are different from each other at low temperature unlike that for Zn doped samples, clearly indicating a transition to a spin-glass like phase. No anomalies were found in Ca- or Pb-doped samples.

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