Field Induced Valence Transition of Eu-based Compounds

铕基化合物的场诱导价态跃迁

• 批准号: 07640472
• 负责人: WADA Hirofumi
• 金额: $ 1.47万
• 依托单位: KYOTO UNIVERSITY
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 1995
• 资助国家: 日本
• 起止时间: 1995 至 1996
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-07640472/
• 关键词: Intermediate valence; Rare earth; Field-induced valence transition; Metamagnetism; High field; Eu; ユーロビウム

Some Eu compounds are known to show intermediate valence between Eu^<2+> and Eu^<3+> configurations. One of the important features of Eu systems is that they exhibit strong temperature dependence of the mean valence. Considering a large difference of magnetic moment between the divalent (7muB) and trivalcnt (0) states, the Eu valence must be affected by high magnetic fields. We have investigated the magnetic field effects on the Eu valence in this research. The following results were obtained.1) The compound EuPd_2Si_2 undergoes a precipitous, yet continuous, valence change at around 170K.We have found that this compound shows a metamagnetic transition under ultra-high filed of 93 T at 10 K.The saturation magnetization is about 7 mu B,which is in agreement with the theoretical value to the divalent state of Eu. This indicates that the metaganetic transition is a valence transition induced by high magnetic fields. This is the first example of this kind of transition found in the Eu-base … More d systems. The metamagnetic transition is accompanied with a large hysteresis, indicating a first order phase transition. This is in contrast to the continuous change of the valence in the temperature dependence.2) The substitution of Pt for Pd decreased the valence transition field (Hv) without broading the transition. It was found that the valence transition temperature (Tv) is proportional to Hv.3) Similar valence transition was observed in EuNi_2 (Sil_<1-x>Ge_x) _2 with 0.75*x*0.82. Especially, Hv of the compond with x=0.75 is lower than 45T,which can be generated by a long pulse magnet. The temperature dependence of the mean valence was studied. The linear relation between Hv and Tv is also observed in this system.4) We have discussed the field-induced valence transition in terms of the interconfigurational fluctuation (ICF) model by taking into account the Zeeman energy of the excited state. A satisfying description has been provied. Especially, we have demonstrated that a first order valcnce transition could be induced by magnetic field, even if the system shows a continuous valence transition against temperature. Less

已知一些Eu化合物显示Eu^<2+>和Eu^<3+>构型之间的中间价态。Eu体系的一个重要特征是其平均价态具有很强的温度依赖性。考虑到二价态（7 μ B）和三价态（0）之间的磁矩差异很大，Eu的价态必须受到强磁场的影响。在本研究中，我们研究了磁场对Eu价态的影响。结果表明：1）EuPd_2Si_2在170 K附近发生了急剧而连续的价态变化，在10 K、93 T的超高磁场下，该化合物发生了变磁转变，饱和磁化强度约为7 μ B，与Eu的二价态的理论值相一致。这表明变晶转变是由强磁场引起的价态转变。这是在Eu基中发现的第一个这种转变的例子 ...更多信息 D系统。变磁性转变伴随着大的磁滞回线，表明是一级相变。这与温度依赖性的价态连续变化相反。2）Pt取代Pd降低了价态跃迁场（Hv），但没有加宽跃迁。3）EuNi_2（Sil_<1-x>Ge_x）_2在0.75*x*0.82时也有类似的价态转变。特别是x=0.75的化合物的Hv低于45T，可由长脉冲磁体产生。研究了平均价态的温度依赖性。在此体系中，Hv与Tv之间也存在线性关系。4）我们利用考虑激发态塞曼能量的组态间涨落（ICF）模型讨论了场诱导的价态跃迁。提供了令人满意的描述。特别地，我们证明了即使体系呈现随温度变化的连续价态跃迁，磁场也能诱导一级价态跃迁。少

项目成果

A.Mitsuda et al.: "Field Induced Valence Transition of Eu(Pd_<1-x>Pt_x)_2Si_2" Phys.Rev.B. 55(印刷中). (1997)

A.Mitsuda 等人：“Eu(Pd_<1-x>Pt_x)_2Si_2 的场诱导价态跃迁”Phys.Rev.B（出版中）。

A.Mitsuda, H.Wada, M.Shiga, H.Aruga Katori and T.Goto: "Field-Induced Valence Transition of Eu (Pd_<1-x>Pt_x) _2Si_2" Phys.Rev.B. 55-17 (in press). (1997)

A.Mitsuda、H.Wada、M.Shiga、H.Aruga Katori 和 T.Goto：“Eu (Pd_<1-x>Pt_x) _2Si_2 的场诱导价态跃迁”Phys.Rev.B。

H.Wada et al.: "First-Order valence Transition of EuPd2Si2 Induced by High Magnetic Fields" J.Phys.Soc.Japan. 65(11). 3471-3473 (1996)

H.Wada 等人：“高磁场诱导的 EuPd2Si2 的一阶价态跃迁”J.Phys.Soc.Japan。

A.Mitsuda et al.: "Field Induced Valence Transition of Eu (Pd_<1-x>Pt_x)_2Si_2" Phys.Rev.B. 55(17)(印刷中). (1997)

A.Mitsuda 等人：“Eu (Pd_<1-x>Pt_x)_2Si_2 的场诱导价态跃迁”Phys.Rev.B. (1997 年出版)。

H.Wada, A.Mitsuda, M.Shiga, H.Aruga Katori and T.Goto: "First-Order Valence Transition of EuPd_2Si_2 Induced by High Magnetic Field" J.Phys.Soc.Japan. 65-11. 3471-3473 (1996)

H.Wada、A.Mitsuda、M.Shiga、H.Aruga Katori 和 T.Goto：“强磁场诱导的 EuPd_2Si_2 的一阶价态跃迁”J.Phys.Soc.Japan。