Pressure induced Novel quantum phenomena in Q2D Mott transition system Ca_2RuO_4

Q2D莫特跃迁体系Ca_2RuO_4中压力诱导的新量子现象

基本信息

批准号：
17540328
负责人：
NAKAMURA Fumihiko
金额：
$ 2.24万
依托单位：
HIROSHIMA UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2005
资助国家：
日本
起止时间：
2005 至 2006
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-17540328/
关键词：
strongly correlated electron pressure effect Ru oxides Mott transition system Quantum Critical Point Giant magnetoresistance Itinerant ferromagnetism

项目摘要

To explore novel quantum phenomena such as unconventional superconductivity, itinerant magnetism, and large magnetoresistance effect is one of the most important and interesting subjects in condensed matter physics. Much attention has been paid for a Mott transition system in single-layered ruthenate oxides. This is because the materials display versatile quantum phenomena, ranging from an antiferromagnetic (AF) Mott insulator to a ferromagnetic (FM) metal, as well as the superconductor. In particular, the pressure phase diagram is quite unique and different from that of the doped system. In this project, we feature two interesting phenomena as follows :1. Anisotropic giant magnetoresistance effect in the vicinity of Mott transitionWe have observed an anisotropic and giant magnetoresistance (MR) of a 4d-electron system Ca_2RuO_4 in the vicinity of a pressure induced Mott transition. At〜2GPa, the MR effect at 10T reaches〜-80% at〜T_c for longitudinal and 〜+80% at low temperatures for the transverse effects. The negative MR is interpreted as a reduction of a FM spin fluctuation at T_c. In contrast, the observed large positive effect is rare and likely due to metal-nonmetal transition induced by applying fields along the c axis.2. Itinerant ferromagnetism in the quasi-2D metallic stateWe reveal that pressurisation to Ca_2RuO_4 transforms it from a Mott insulator with an AF ground state to a quasi-2D metal with a FM ground state. This ferromagnetism has been observed in the metallic phase, and then contains features of an itinerant FM. Firstly, M_<rem>〜35μ_B is quite smaller than the saturated moment of 2μ_B of localised Ru^<4+> ion. Secondly, a ratio of p_<eff> / M_<rem>〜5 is much larger than 1 of localized spins systems. Lastly, M is not easily saturated with H. In particular, the magnetisation process at low temperatures exhibits good linearity in an Arrott plot (M_<rem>^2 versus H/M plot). These FM natures are comparable to typical itinerant ferromagnet of MnSi.

探索新颖的量子现象，例如非常规超导性，巡回磁性和较大的磁性效应，是凝结物理学中最重要，最有趣的主题之一。对单层鲜烯酸氧化物中的莫特过渡系统已经引起了很多关注。这是因为材料显示出多功能的量子现象，范围从抗铁磁（AF）Mott绝缘子到铁磁（FM）金属以及超导体。特别是，压力相图与掺杂系统的压力相图非常独特，并且不同。在这个项目中，我们具有两个有趣的现象，如下所示：1。各向异性巨磁磁性在Mott Transition我们附近观察到了4D电子系统CA__2RUO_4在压力诱导Mott Transition的附近的各向异性和巨型磁阻（MR）。在〜2GPA时，纵向的MR效应在〜t_c时达到〜-80％，在横向作用下低温下〜80％的MR效应。负MR被解释为在T_C处的FM自旋波动的减少。相比之下，观察到的较大的正效应很少，并且可能是由于沿C轴施加磁场引起的金属非金属跃迁引起的。2。准2D金属状态中的巡回铁磁学表明，加压到CA_2RUO_4将其从具有AF基态的Mott绝缘子转变为具有FM接地状态的准2D金属。在金属阶段已经观察到了这种铁磁学，然后包含巡回FM的特征。首先，M_ <rem> 〜35μ_b非常小于局部ru^<4+>离子的饱和矩。其次，p_ <eff> / m_ <rem> 〜5的比率大于局部旋转系统的比率大得多。最后，M不容易被H饱和。这些FM本质与MNSI的典型巡回铁磁相媲美。

项目成果

期刊论文数量（18）

专著数量（0）

科研奖励数量（0）

会议论文数量（0）

专利数量（0）

Pressure-induced Mott transition and related novel quantum phenomena in Ca2Ru04

Ca2Ru04 中压力诱导的莫特跃迁及相关新量子现象

DOI：
发表时间：
2007
期刊：
J. Phys. Soc. Jpn. 76 (in press)
影响因子：
0
作者：
F.Honda;N.Metoki;K.Kaneko;S.Jonen;E.Yamamoto;D.Aoki;Y.Homma;Y.Haga;Y.Shiokawa;Y.Onuki;Koji Ueda et al.;Fumihiko Nakamura
通讯作者：
Fumihiko Nakamura

Magnetic heat transport in RcCuO4 (R=La, Pr, Nd, Sm, Eu, and Gd)

RcCuO4 中的磁热传输（R=La、Pr、Nd、Sm、Eu 和 Gd）