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STUDY OF THE PHASE TRANSITION BY THE MAGNETOSTRICTION MEASUREMENT UNDER A PULSED HIGH MAGNETIC FIELD

脉冲强磁场下磁致伸缩测量相变的研究

基本信息

批准号：
06640477
负责人：
TAKEUCHI Tetsuya
金额：
$ 1.34万
依托单位：
Osaka University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1994
资助国家：
日本
起止时间：
1994 至 1995
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-06640477/
关键词：
MAGNETOSTRICTION PULSED HIGH MAGNETIC FIELD CAPACITANCE METHOD THERMAL EXPANSION HEAVY FERMION KONDO EFFECT QUADRUPOLE 強磁場

项目摘要

The aim of this research project is to study the phase transition by the magnetstriction measurement under a pulsed high magnetic field. The principle of the measurement is the high sensitive three terminal method. For the test measurement, we constructed the magnetostriction cryostat for the measurement in a static magnetic field up to 8 T and thermal expansion cryostat. The temperature range is 1.8 K to 300 K.The system for the pulse field is under construction. Here we report the several results which has been obtained from the static field measurements.1.Antiferromagnetic transition and volume effect in Ce(Ru_<1-x>Rh_x)_2Si_2This compound has an antiferromagnetic ordering at 5.5 K and shows metamagnetic transitions at 3.5 and 6 T.From the neutron scattering measurements, it has been found that this antiferromagnetic ordering is the SDW transition having the magnetic wave vector along the c-axis. Electrical resistivity along the c-axis shows a large bump (about 30%) below the Neel t … More emperature, while in the a-axis, however, resistivity decreases as T^2 law with decreasing the temperature. From these results, it is concluded that the SDW transition is caused by the nesting effect of a part of Fermi surface along the c-axis. The anisotropic gap opens by the SDW transition. The thermal expansion shows a rapid decrease of the lattice constant below 50 K where the Kondo effect takes place. Below the Neel temperature, however, the rapid decrease of the lattice constant desappears and the lattice constant becomes almost constant. This result may imply that the INVAR and/or anti-INVAR effect due to the moment-volume instability does exist in 4f heavy electron systems.Magnetostriction in the SDW phase ia very small as the nomal metal. Above the critical field where the SDW is quenched, the unit cell volume rapidly increases with increasing the magnetic field. This large magnetostriction is characteristic for the heavy fermion compounds and indicates that the Kondo fluctuation still remains above the critical field.2.Anisotropic thermal expansion and field-induced structural phase transition in PrCu_2Thermal expansion in PrCu_2 is very anisotropic due to the highly anisotropic crystalline electric field. The metamagnetic transition is caused by a large modification of the crystalline electric field coming from a field induced structural phase transition. This structural phase transition probably come from the quadrupole-quadrupole interactions. Less

本研究的目的是通过测量脉冲强磁场下的磁致伸缩来研究相变。测量原理是高灵敏度的三端法。对于测试测量，我们构建了磁致伸缩低温恒温器，用于在高达8 T的静磁场和热膨胀低温恒温器中进行测量。温度范围为1.8 K至300 K。脉冲场系统正在建设中。本文报道了静态场测量的几个结果：1. Ce（Ru_Rh_x）_2Si_2中的反铁磁转变和体积效应。该化合物在5.5K时具有反铁磁有序，在3.5和6T时出现变磁转变。<1-x>已经发现，这种反铁磁有序是具有沿着c轴的磁波矢量的SDW转变。沿着c轴的电阻率示出了低于Neel t的大隆起（约30 ...更多信息而在a轴方向上，电阻率随温度的降低而按T^2规律减小。从这些结果可以得出结论，SDW转变是由费米面沿着c轴的一部分嵌套效应引起的。各向异性间隙通过SDW转变打开。热膨胀表明晶格常数在低于50 K时迅速减小，其中近藤效应发生。然而，低于Neel温度，晶格常数的快速减小消失，晶格常数变得几乎恒定。这一结果可能意味着在4f重电子系统中确实存在由动量-体积不稳定性引起的INVAR和/或反INVAR效应，SDW相的磁致伸缩与正常金属一样很小。在SDW被淬灭的临界场以上，晶胞体积随着磁场的增加而迅速增加。这种大的磁致伸缩是重费米子化合物的特征，表明在临界场以上，近藤涨落仍然存在。2. PrCu_2的各向异性热膨胀和场致结构相变PrCu_2的各向异性热膨胀是非常各向异性的，这是由于高度各向异性的晶体电场。变磁转变是由场致结构相变引起的晶体电场的大的修改引起的。这种结构相变可能来自四极-四极相互作用。少