Exotic Electronic Phenomena of the Low-Carrier System Ce-Monopnictides : From Localized to Itinerant

低载流子系统Ce-Monopnictides的奇异电子现象:从局部到巡回

基本信息

批准号：
14340107
负责人：
KOHGI Masahumi
金额：
$ 9.54万
依托单位：
TOKYO METROPOLITAN UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2002
资助国家：
日本
起止时间：
2002 至 2004
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-14340107/
关键词：
CeP Ce monopnictides neutron diffraction X-ray diffraction low-carrier system p-f mixing magnetic polaron X線解析少数キャリアー系 P-f mixing

项目摘要

The purpose of the present research is to clarify the physics behind the novel phenomena exhibited by the low-carrier systems Ce-monopnictides by neutron scattering and X-ray diffraction. The main results of the project are as follows :(1)We have revealed by neutron diffraction under high pressures that the magnetic state of CeP at the pressures above 3.2 GPa is ferromagnetic at low temperatures in spite that the magnetic phase diagram below about 3 GPa is very complex with long period magnetic structures with the periods of 9,8,7,6,5,4,3 Ce (001) planes with increasing pressure. We found also that the saturation magnetic moment of a Ce atom in the ferromagnetic state decreases with increasing pressure above 3.2 GPa. (2)We established by utilizing synchrotron radiation X-ray diffraction technique that CeP shows long period magnetic structures with the periods of 11,10,9,8 Ce (001) planes with increasing magnetic field up to 14 T. The result shows that the the magnetic field plays a similar role as the pressure on the appearance of the exotic magnetic states of CeP. (3)The X-ray diffraction experiments under high pressure revealed that the lattice constant of CeP increase in the ferromagnetic state at the pressures above about 3GPa whereas it decreases in the ordered state under pressure below 3 GPa. This fact together with the reduction of the ordered moment at the pressures above 3GPa indicates that 4f electron state of CeP changes its nature from an localized one to an itinerant one at the pressure above about 3 GPa.These findings support the idea that the main parameter to govern the exotic properties of Ce-monopnictides is the carrier density in the system, and that the varieties of the exotic properties observed for Ce-monopnictides are predominantly due to the difference of the intrinsic carrier densities of the materials as well as to their change by applying external magnetic field or pressure.

本研究的目的是通过中子散射和 X 射线衍射阐明低载流子系统 Ce-单硝化物所表现出的新现象背后的物理原理。该项目的主要成果如下：(1)通过高压下的中子衍射揭示了CeP在3.2 GPa以上压力下的磁态在低温下是铁磁性的，尽管在3 GPa以下的磁相图是非常复杂的长周期磁结构，随着压力的增加，9,8,7,6,5,4,3 Ce (001) 平面的周期。我们还发现，铁磁态 Ce 原子的饱和磁矩随着压力增加到 3.2 GPa 以上而减小。 (2)利用同步辐射X射线衍射技术，我们发现CeP在磁场强度增加至14 T时表现出周期为11,10,9,8 Ce(001)面的长周期磁结构。结果表明：磁场对 CeP 奇异磁态的出现起着与压力类似的作用。 (3)高压下的X射线衍射实验表明，在高于3GPa的压力下，CeP在铁磁态下晶格常数增大，在低于3GPa的压力下在有序态下晶格常数减小。这一事实与压力高于 3 GPa 时有序矩的减小一起表明，CeP 的 4f 电子态在压力高于约 3 GPa 时其性质从局域电子态变为巡回电子态。这些发现支持了以下观点：主要参数控制 Ce-monopnictides 的奇异特性的是系统中的载流子密度，并且观察到 Ce-monopnictides 的奇异特性的变化主要是由于材料的本征载流子密度的差异：以及通过施加外部磁场或压力来改变它们。