Nuclear Magnetic Resonance Study on the Charge Density Wave (CDW) in Copper Sulfide Spinel CuV_2S_4

硫化铜尖晶石CuV_2S_4中电荷密度波(CDW)的核磁共振研究

• 批准号: 09640439
• 负责人: KISHIMOTO Yutaka
• 金额: $ 1.92万
• 依托单位: University of Tokushima
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 1997
• 资助国家: 日本
• 起止时间: 1997 至 1998
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-09640439/
• 关键词: Copper Sulfide; Spinel-type Compound; CuV_2S_4; Charge Density Wave (CDW); NMR; Spin-Lattice Relaxation; Knight Shift; High T_c Superconductor; 電荷密度波(CDW); 核磁気共鳴(NMR); 緩和率

CuV_2S_4 shows the charge density wave (CDW) transition which is a typical low dimensional property although CuV_2S_4 is a three dimensional substance. At high temperatures, all the ^<63>Cu, ^<65>Cu and ^<51>V spin-lattice relaxation rates obey the Korringa law, and CuV_2S_4 is considered to be a simple metal at high temperatures. ^<51>V relaxation rate shows the Arrhenius type temperature dependence below 90 K, which indicates an energy gap due to CDW.Below 75 K, ^<51>V relaxation rate obeys the Korringa law again, which indicates its energy gap is anisotropic. The ratio of ^<63>Cu and ^<65>Cu relaxation rates is close to the square of the ratio of their gyromagnetic ratios at high temperatures, which tells us its relaxation mechanism is magnetic and is consistent with obeying the Korringa law. But with approaching CDW transition temperature, it reverses and becomes the square of the ratio of their quadrupole moments. The ^<63>Cu and ^<65>Cu relaxation rate becomes to diverge at CDW transition temperature, which indicates that the electric field gradients at Cu site becomes larger. This fact agrees with the fact that ^<63>Cu and ^<65>Cu NMR spectra disappear due to CDW below 83 K.^<51>V Knight shift ^<51>K is negative at high temperatures because the core polarization is effective due to V 3d electrons. The magnitude of ^<51>K becomes smaller with approaching CDW transition temperature and changes to a positive value after CDW transition, which indicates that the paired two electrons are distributed in each CDW wave length. The hyperfine coupling constant of Cu is positive, which seems to indicate the existence of the super transferred hyperfine coupling in CuV_2S_4 as observed in copper oxide high T_c superconductors.

CUV_2S_4显示了电荷密度波（CDW）过渡，这是典型的低维属性，尽管CUV_2S_4是三维物质。在高温下，所有 ^<63> cu， ^<65> cu和 ^<51> v旋转静止放松率遵守Korringa定律，而CUV_2S_4被认为是高温下的简单金属。 ^<51> v松弛率显示了低于90 K的Arrhenius型温度依赖性，这表明由于CDW而引起的能量差距。BELOW75 K， ^<51> V松弛率再次遵守Korringa定律，这表明其能量差距是偏置的。 ^<63> Cu和 ^<65> Cu松弛速率的比率接近其高温下其陀螺仪比率之比的平方，这告诉我们其弛豫机制具有磁性，并且与遵守Korringa定律一致。但是，随着CDW过渡温度的接近，它逆转并成为其四极矩比率的平方。 ^<63> Cu和 ^<65> Cu松弛率在CDW过渡温度下变化，这表明CU位点的电场梯度变得更大。这一事实与以下事实相符： ^<63> cu和 ^<65> cu nmr光谱由于CDW以下低于83 k。随着CDW过渡温度的接近， ^<51> k的大小变小，并在CDW过渡后变为正值，这表明配对的两个电子在每个CDW波长中分布。 Cu的超精细耦合常数为正，这似乎表明了在CUV_2S_4中超级转移的超精细耦合的存在，如在铜氧化物高T_C超导体中所观察到的。

项目成果

T.Ohno, K.Koyama and H.Yasuoka: "Cu NQR and Hole Transfer in Y_<1-x>Pr_xBa_2Cu_3O_<7->δ" Physica B. 237-238. 100-102 (1997)

T.Ohno、K.Koyama 和 H.Yasuoka：“Y_<1-x>Pr_xBa_2Cu_3O_<7->δ 中的 Cu NQR 和空穴转移”Physica B. 237-238 (1997)。

T.Ohno and Y.Kishimoto: "^<63>Cu and ^<51>V spin-spin relaxation rates in CuV_2S_4" Physica B. (in press). (1999)

T.Ohno 和 Y.Kishimoto：“CuV_2S_4 中的 ^<63>Cu 和 ^<51>V 自旋-自旋弛豫率”Physica B.（正在出版）。

Y.Kishimoto, T.Ohno et al.: "^<51>V Knight Shift of a C15 Laves Phase Superconductor HfV_2" Physica B. 237-238. 312-314 (1997)

Y.Kishimoto、T.Ohno 等人：“C15 Laves 相超导体 HfV_2 的^<51>V Knight Shift”Physica B.237-238。

T.Ohno, K.Koyama and H.Yasuoka: "CuNQR and Hole Transfer in R_<1-x>Pr_xBa_2Cu_3O_<7-delta>" Physica B. 237-238. 100-102 (1997)

T.Ohno、K.Koyama 和 H.Yasuoka：“R_<1-x>Pr_xBa_2Cu_3O_<7-delta> 中的 CuNQR 和空穴转移”Physica B. 237-238。

Y.Kishimoto, T.Ohno, T.Kanashiro, T.Takai, K.Nakamura, K.Sumiyama, T.Hihara and K.Suzuki: "^<51>V Knight Shifts in the Superconducting State of V_3Si" J.Magn.Magn.Mat.177-181. 367-368 (1998)

Y.Kishimoto、T.Ohno、T.Kanashiro、T.Takai、K.Nakamura、K.Sumiyama、T.Hihara 和 K.Suzuki：“^<51>V_3Si 超导态中的 V Knight 转变” J.Magn