Impurity Effect and Size Effect on Itinerant-Electron Ferromagnets

巡回电子铁磁体的杂质效应和尺寸效应

• 批准号: 04640353
• 负责人: OGAWA Shinji
• 金额: $ 0.51万
• 依托单位: Tokyo Denki 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: 1992
• 资助国家: 日本
• 起止时间: 1992 至 1994
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-04640353/
• 关键词: Itinerant-electron ferromagnetism; Itinerant-electron metamagnetism; Magnetic impurity effect; Zirconium-zinc ferromagnetic compound; Yttrium-nickel ferromagnetic alloy; Cobalt disulphide-diselenide; 遍歴電子強磁性; パイライト型コバルト化合物; 磁気熱膨張; 強磁性体の不純物効果; イッ

Effect of doping gadlinium atoms into weak itinerant-electron ferromagnets or substituting a part of constituent metal atoms for different transition-metal atoms in weak itinerant-electron ferromagnets have been studied experimentally for ZrZn_2, YNi_3, Y_2Ni_7 ferromagnets. Effect of substituting anions in CoS_2 ferromagnet on its magnetic property has also been examined. Measuremnts have been made of magnetization curves in a very strong magnetic field. The temperature variation of magnetization in the Gd-doped weak itinerant-electron ferromagnets can be explained by taking into consideration of the induced magnetic moment in itinerant-electrons due to localized spins, on the basis of the mean field approximation. However, the magnetic field dependence of magnetization shows an inadequacy of the mean field approximation and suggests the effect of field on spin fluctuations to suppress and also an effect of anisotropy. The substitution by transition-metal atoms appears to shift a Fermi level as a first order approximation, but some complicated band structure effet seems to dominate the variaton of magnetization. The substitution of selenium for sulphur results in a drastic change of magnetic states in the itinerant-electron ferromagnet CoS_2. It appears a change from a ferromagnet to an itinerant-electron metamagnet, and further to a paramagnet by the substitution. Especially, in the 10 % substituted sample, it has been observed a clear first order phase transiton from ferromagnetic state to a metamagnetic state and a second order phase transiton from a metamagnetic state to a paramagnetic state by increasing a temperature. This is due to a quite homogeneous state of our samples. This transiton can be qulitatively analyzed by the Landau's theory of phase transiton. A possible size effect in the very weak itinerant-electron ferromagnets has been examined experimentally, but no appreciable change has been observed.

对ZrZn_2，YNi_3，Y_2Ni_7弱巡游电子铁磁体进行了实验研究。本文还考察了CoS_2铁磁体中阴离子的取代对其磁性能的影响。测量了在强磁场中的磁化曲线。在平均场近似的基础上，通过考虑局域自旋在巡游电子中产生的感生磁矩，可以解释Gd掺杂弱巡游电子铁磁体的磁化强度随温度的变化.然而，磁化强度的磁场依赖性显示了平均场近似的不足，并建议抑制场对自旋涨落的影响以及各向异性的影响。在一级近似下，过渡金属原子的替代似乎使费米能级移动，但某些复杂的能带结构效应似乎支配着磁化强度的变化。硒取代硫导致巡游电子铁磁体CoS_2的磁态发生剧烈变化。它表现为从铁磁体到巡游电子变磁体的转变，并通过替代进一步转变为顺磁体。特别地，在10%取代的样品中，已经观察到从铁磁态到变磁态的明显的一级相变和从变磁态到顺磁态的二级相变。这是由于我们的样品具有相当均匀的状态。这种相变可以用朗道的相变理论进行定量分析。在实验上研究了很弱的巡游电子铁磁体中可能存在的尺寸效应，但没有观察到明显的变化。

项目成果

S.Ogawa: "Magnetic measurement at ultra-low temperature and in high magnetic field" Jpn. J.Appl. Phys. Series. vol.8. 220-222 (1993)

S.Okawa：“超低温和强磁场下的磁测量”Jpn。

小川 信二: "Magnetic measurement at ultra-low tempearture and in high magnetic field" Japanese Journal of Applied Physics Series. 8. 220-222 (1993)

Shinji Okawa：“超低温和高磁场下的磁测量”日本应用物理杂志系列，8. 220-222 (1993)。