NMR study in a half-metallic system, Sr2FeMoO6
NMR study in a half-metallic system, Sr2FeMoO6
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DOI：
10.1016/j.jmmm.2006.11.008
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发表时间：
2007-03
影响因子：
2.7
通讯作者：
K. Ohno;H. Kato;T. Nishioka;M. Matsumura
中科院分区：
文献类型：
--
作者：
K. Ohno;H. Kato;T. Nishioka;M. Matsumura
为了阐明有序参数的对称性或超导电性的微观起源，对水合Co氧化物NaxCoO 2·yH 2 O（或NaxCoO 2·yD 2 O）和母体NaxCoO 2进行了多晶和单晶样品的NMR/NQR、中子散射和各种其它测量。的NMR奈特位移被抑制的SC的发生为两个磁场方向，平行和垂直于CoO 2平面，表明库珀对是在单重态。Na0.44CoO2的非弹性中子散射数据表明，在倒易空间Q点存在弱的自旋涨落，对应于面内和面间的磁关联，而在超导体NaxCoO 2·yD 2 O的大单晶的非弹性散射数据中没有检测到铁磁涨落.在磁有序相的Na 0.5CoO2确定的磁结构表明，在CoO 2平面内的磁相关基本上是反铁磁的。由非磁性杂质的Tc抑制率太小，不能用各向同性序参数来解释。这些结果表明，NaxCoO_2·yH_2O中实现了单重态SC。只有核弛豫率1/T_（1/T_（1/T_（1）对T的曲线没有明确的相干峰的结果，不能简单地用各向同性序参量来解释。
NMR/NQR, neutron scattering, and various other kinds of measurements have been carried out for hydrated Co oxides NaxCoO2·yH2O(or NaxCoO2·yD2O), and the mother system NaxCoO2by using both polycrystalline and single-crystal samples, to clarify the symmetry of the order parameter or the microscopic origin of the superconductivity (SC). The NMR Knight shifts are suppressed by the occurrence of the SC for both magnetic field directions, parallel and perpendicular to the CoO2planes, indicating that the Cooper pairs are in the singlet state. Inelastic neutron scattering data of Na0.44CoO2indicate the existence of weak spin fluctuations at Q points in the reciprocal space corresponding to both intra-plane and inter-plane magnetic correlations, while no indication of the ferromagnetic fluctuations has been detected in the inelastic scattering data taken for large single crystals of the superconducting NaxCoO2·yD2O. The magnetic structure determined in the magnetically ordered phase of Na0.5CoO2indicates that the magnetic correlation is basically antiferromagnetic within a CoO2plane. The rate of the Tc-suppression by non-magnetic impurities is too small to be explained by considering isotropic order parameters. All these results indicate that the singlet SC is realized in NaxCoO2·yH2O. Only the result that the curve of the nuclear relaxation rate 1/T1plotted against T does not have a definite coherence peak, cannot simply be explained by the isotropic order parameter.