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Reinvestigation of spin-density wave of metallic Cr by neutron scattering-Search for a connection to stripe order--

通过中子散射重新研究金属Cr的自旋密度波-寻找与条纹序的联系--

基本信息

批准号：
16540303
负责人：
HIRAKA Haruhiro
金额：
$ 2.3万
依托单位：
Tohoku University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2004
资助国家：
日本
起止时间：
2004 至 2005
项目状态：
已结题

项目摘要

1. We characterized novel low-energy magnetic excitations of Cr, so-called Fincher-Burke mode (FB-mode), by neutron inelastic scattering. Surprisingly, both the magnetic-peak intensity and the magnetic-dispersion relation are found to be asymmetric about the magnetic-zone center. Another single crystal of Cr reproduces this prominent feature using different instrumental resolutions, and the asymmetry becomes less significant with increasing temperature. Thus, we concluded that such the asymmetry is an intrinsic nature of the FB mode, or that there is another factor governing this asymmetry (e. g. chirality). In order to investigate further, we tried to observe Mn/V-impurity effects on the FB mode. We succeeded in growing such the single crystals in 1-mm size by arc-melting techniques. By tuning the growing condition, it will be able to grow impurity-doped crystals up to 10 mm for inelastic neutron scattering experiments.2. Through Ni-impurity doping onto La2-xSrxCuO4 (LSCO), we found that carrier concentration governs magnetic correlations as well as electric transport. This is analogous to the case of impurity doping on Cr, in which the incommensurability of spin correlations is proportional to impurity concentration (or, band-electron density). However, no magnetic excitations like the FB mode in Cr are observable yet in LSCO. It is necessary to narrow an argument whether there are no such magnetic excitations intrinsically, the cross section is just small to detect, or S(Q, E) is quite different between Cr and LSCO.3. During the course of neutron-scattering research for Cr and LSCO, a high S/N ratio and a fine Q resolution are required in neutron spectrometer. We developed a new technique that uses a combination of a Ge monochromator and a pylorytic-graphite analyzer in inelastic scattering measurements. In fact, we succeeded in observing quasi-particle excitations, such as phonons and magnons, for Cr and LSCO with high Q resolutions and reasonable statistics.

1.我们的特点是新的低能量的Cr的磁激发，所谓的Fincher-Burke模式（FB模式），中子非弹性散射。令人惊讶的是，磁峰强度和磁色散关系被发现是不对称的磁区中心。另一种单晶的铬再现这一突出的特点，使用不同的仪器分辨率，和不对称性变得不那么重要，随着温度的升高。因此，我们得出结论，这种不对称性是FB模式的固有性质，或者存在另一个控制这种不对称性的因素（例如，G.手性）。为了进一步研究，我们试图观察Mn/V杂质对FB模式的影响。我们成功地生长这样的单晶在1毫米大小的电弧熔化技术。通过调节生长条件，可以生长出直径达10 mm的杂质掺杂晶体，用于中子非弹性散射实验.通过对La_（2-x）Sr_xCuO_4（LSCO）的Ni杂质掺杂，我们发现载流子浓度不仅影响电输运，而且也影响磁关联。这类似于在Cr上掺杂杂质的情况，其中自旋相关的不可逆性与杂质浓度（或带电子密度）成比例。然而，在LSCO中还没有观察到像Cr中的FB模式的磁激发。有必要缩小一个论点是否有这样的磁激励本质上，只是小的横截面检测，或S（Q，E）是相当不同的Cr和LSCO。在研究Cr和LSCO的中子散射过程中，对中子谱仪的信噪比和Q分辨率提出了很高的要求。我们开发了一种新的技术，在非弹性散射测量中使用Ge单色仪和pylorytic-graphite分析仪的组合。事实上，我们成功地观察到了Cr和LSCO的准粒子激发，例如声子和磁振子，具有高Q分辨率和合理的统计数据。