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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射线衍射来阐明低载流子系统Ce-铌酸盐所表现出的新现象背后的物理机制。（1）高压中子衍射结果表明，CeP在3.2GPa以上的压力下，低温下的磁态为铁磁态，而在3GPa以下的压力下，其磁相图非常复杂，具有9，8，7，6，5，4，3Ce（001）面周期的长周期磁结构。我们还发现，在铁磁态的Ce原子的饱和磁矩随压力的增加而减小超过3.2 GPa。(2)We利用同步辐射X射线衍射技术证实了CeP在14 T的磁场下具有11，10，9，8 Ce（001）面周期的长周期磁性结构。结果表明，磁场对CeP奇异磁态的产生起着与压力相似的作用。（3）高压下的X射线衍射实验表明，CeP在铁磁态时的晶格常数在压力高于3GPa时增大，而在有序态时的晶格常数在压力低于3GPa时减小。这一事实以及在3GPa以上的压力下有序矩的减小表明CeP的4f电子态在3GPa以上的压力下从定域态转变为巡游态.这些发现支持了控制Ce-稀土氧化物奇异性质的主要参数是系统中的载流子密度的观点. Ce-铌酸盐的奇异性质的变化主要是由于材料的本征载流子密度的差异以及它们在外加磁场或压力下的变化。