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Magnetism and Spin Fluctuations of Frustrated YMn_2.

受抑YMn_2的磁性和自旋涨落。

基本信息

批准号：
02452038
负责人：
SHIGA Masayuki
金额：
$ 4.29万
依托单位：
Kyoto University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (B)
财政年份：
1990
资助国家：
日本
起止时间：
1990 至 1991
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-02452038/
关键词：
Laves Phase YMn_2 Frustration Spin glass Spin liquid NMR Antiferromagnetism ラ-ベン相

项目摘要

Laves phase intermetallic compounds YMn_2 is an antiferromagnet with a complicated spin structure with a geometrical frustration of magnetic interaction. Substitution of Sc for Y collapses the antiferromagnetic ordering and gives rise to the paramagnetic ground state. The paramagnetic Y (Sc) Mn_2 exhibits giant spin fluctuations and strong enhancement of the low temperature specific heat coefficient. In this research, we study the ground state properties of this system and effects of impurity doping in order to know the role of spin frustrations. We also study the magnetic and other properties of 6-Mn-Al alloys in the same interests. We have got following results in this study.(1) It has been revealed that Y (sc) (Mn_<1-x>Al_x) _2 system becomes spin-glass by substitution of Al for Mn and the specific heat coefficient rapidly decreases with increasing Al concentration. The temperature dependence of electric resistivity of Al substituted alloys exhibits the Kondo type resistance minimum, indicating localization Mn moments. We interpreted these results as follow : A spin liquid state is formed as a result of frustration. Substitution of Al for Mn raise the degeneracy due to frustration, leading spin glass state.(2) Similar results have been obtained as above.(3) We have successfully set up the coherent type NMR spectrometer, which will contribute to obtain microscopic information to prove the present model.

Laves相金属间化合物YMn2是一种反铁磁体，具有复杂的自旋结构，具有几何上的磁相互作用障碍。Sc取代Y使反铁磁有序崩塌，产生顺磁基态。顺磁性的Y(Sc)Mn2表现出巨大的自旋涨落和低温比热系数的强烈增强。在本研究中，我们研究了该系统的基态性质和杂质掺杂的影响，以了解自旋受挫的作用。同样，我们还研究了6-Mn-Al合金的磁性和其他性质。研究结果表明：(1)Y(Sc)(Mn_t；1-x&gt；Al_x)_2体系通过Al取代Mn而成为自旋玻璃，比热系数随Al浓度的增加而迅速下降。Al替代合金的电阻率随温度的变化呈现近藤型电阻极小值，表明了局域化的Mn矩。我们对这些结果的解释如下：受挫导致了自旋液态的形成。Al取代Mn提高了由于受挫而产生的简并，导致自旋玻璃态。(2)得到了类似的结果。(3)我们成功地建立了相干型核磁共振谱仪，这将有助于获得微观信息来验证本模型。