THE PHENOMENON OF THE LOW TEMPERATURE STRUCTURAL IN AMORPHOUS ALLOY (Fe_(0.1)Ni_(0.5)Co_(0.4))_(78)Si_8 B_(14)

利用磁导率减落的自动测量仪,测量了非晶合金(Fe_(0.1)Ni_(0.5)Co_(0.4))_(78)Si_8B_(14)等温时效时退磁不能恢复的减落。以此考查了低温结构弛豫动力学行为,计算了弛豫激活能和弛豫谱。结果表明,低温结构弛豫是平均激活能低的多弛豫过程,在这个过程中发展了化学短程序(CSRO)。     

STRUCTURAL RELAXATION OF AMORPHOUS ALLOYS Fe_(77.8)Si_(7.5)B_(14.7) AND Fe_(78.5)Si_(8.9)B_(12.6)

<正> 本文用Mossbauer技术结合DTA和电阻分析,对两种非晶态合金(Ⅰ)Fe_(77.8)Si_(7.5)B_(14.7)和(Ⅱ)Fe_(78.5)Si_(8.9)B_(12.6)的结构弛豫进行了研究。 Ⅰ和Ⅱ两种非晶态合金的DTA曲线如图1,晶化开始温度分别为530和500℃,晶化前均出现较长的放热峰,预示其结构弛豫过程中可能发生某种结构变化。     

Structural effect of fullerene derivative on polaron relaxation and charge transfer in poly(3-hexylthiophene)/fullerene composite

The structural effect of a side chain in a fullerene derivative on electron relaxation and polaronic charge transfer in a poly(3-hexylthiophene)/fullerene composite was studied by 3 cm waveband electron paramagnetic resonance. All the systems with different fullerene derivatives demonstrate a sum spectrum of small localized and mobile polarons whose contributions depend on the structure of the fullerene derivative. Both the spin–lattice and spin–spin relaxation times were determined separately in a wide (77–320 K) temperature region using the steady-state saturation method. It was shown that spin relaxation, susceptibility and dynamics are governed by the dipole–dipole interaction of the polarons as well as by the structure of the side chains in the fullerene derivative. The treatment of the polymer matrix by the fullerene changes its dimensionality and accelerates polaron diffusion along polymer chains.     

Electronic state of κ-(BMDT-TTF)2Au(CN)2 studied by NMR and thermoelectric measurements

The electronic state of κ-(BMDT-TTF)₂Au(CN)₂ was investigated by measurements of H-NMR¹-NMR and thermoelectric power. In H-NMR,¹-NMR, the profile of the nuclear relaxation curve changed drastically at 75 K from exponential time-dependence to non-single exponential one reflecting inhomogeneous relaxation. This change evidences a transition in the electronic state at this temperature. However, the longest T₁ below the transition temperature behaves like a Korringa law, suggesting that the low-temperature state is another metallic state. The thermoelectric power shows a strong anomaly around 75 K, being consistent with the NMR results. Above that, the temperature dependence is similar to that found in the κ phase of BEDT-TTF compounds, suggesting a similar Fermi-surface topology. These results suggest that the transition at 75 K is not a conventional metal-to-insulator transition but a metal-to-metal transition.     

Observation of the coherence peak of H-NMR-NMR relaxation rate in the superconducting state of (MDT-TTF)2Aul2

We have investigated the superconductivity in the organic conductor, (MDT-TTF)₂Aul₂ (T_c = 4.1 K) from the temperature dependence of H¹ nuclear relaxation rate, 1/T₁, measured by the field cycling method. The nuclear relaxation above 3 K is well characterized by a single relaxation time for nearly two decades. In the normal state, the standard Korringa relation holds. 1/T₁ just below T_c showed a clear enhancement, followed by a falling-oil at lower temperatures. This behavior is just as predicted in the BCS theory (coherence peak) and implies that this material is a conventional superconductor with an isotropic gap. The decay of the nuclear magnetization below 3 K appeared non-sinle exponential. This is explained as the effect of trapped vortices.     

HEAT CAPACITIES OF Fe_（40）Ni_（40）B_（20） GLASSY ALLOY MEASURED BY ENTHALPY METHOD

ＨＥＡＴＣＡＰＡＣＩＴＩＥＳＯＦＦｅ_（４０）Ｎｉ_（４０）Ｂ_（２０）ＧＬＡＳＳＹＡＬＬＯＹＭＥＡＳＵＲＥＤＢＹＥＮＴＨＡＬＰＹＭＥＴＨＯＤ￥ＪＩＡＮＧＱｉｎｇ;ＺＨＡＯＭｉｎｇ;ＬＩＪｉａｎｃｈｅｎ（ＪｉｌｉｎＵｎｉｖｅｒｓｉｔｙｏｆＴｅｃｈｎｏｌ?..     

三元超导化合物Sc_5Ir_4Si_(10)的低温比热性质

在零场下2～300K以及不同磁场下2～10K温度范围内,分别测量了超导Sc5Ir4Si10单晶的比热。采用4-Einstein峰拟合声子谱的方法对高温部分进行处理,成功地分离了Sc5Ir4Si10的晶格比热和电子比热。10K以下的比热遵守经典的超导理论,即晶格比热与温度的三次方成正比,电子比热符合温度的幂指数关系。4K以下电子比热的磁场关系为ΔCe/T∝Hα,其中α与温度有关。随着温度的降低α的值从0.67增大到0.76,表明Sc5Ir4Si10的超导配对可能是s波和d波混合波,并由d波向s波转化。     

Fe55Ni2Cr12Mo10Y2B6C13块体非晶合金的热膨胀行为

本文采用铜模吸铸法制备直径为4mm的块体非晶合金Fe55 Ni2 Cr12 M010 Yo12 B6 C13,对非晶合金在298K-1073K温度区间的热膨胀行为进行了分析.非晶合金的膨胀系数在室温至接近玻璃转化温度区间没有发生明显的变化;当温度超过Tg后,由玻璃态进人过冷液相区,粘度急剧增加,膨胀系数增高;在T>Tg...     

Metastable magnetic behavior in La_(0.9)Tb_(0.1)MnO_3

The linear and nonlinear magnetizations of La_(0.9)Tb_(0.1)MnO_3 at low temperatures were reported in detail.The temperature dependence of magnetization shows peaks at 50,100 and 150 K,respectively.When LaMnO_3 is Tb-doped,its magnetic structure exhibits a canted antiparallel spin order.This is different from classical antiferromagnetic(AFM) in which the relaxation behavior takes place at about 150 K.At 50 K,Tb-doped LaMnO_3 exhibits canonical spin glass behavior,arising from the competition of exchange and super-exchange between spins.The peak at 100 K shows neither spin glass behavior nor canted AFM behavior.Its peak value increases with frequency increasing,and the transition temperature of the peak shifts to higher temperatures with frequency increasing.The study of aging behavior at 100 K shows a periodical variable metastability,which is ascribed to the competition between ferromagnetic(FM)-,AFM-and sinusoidal-order interactions.This work should shed a light on understanding the complex magnetic structure of the nerovskite oxides.     

-NMRC-NMR study on α-(BEDT-TTF)2MHg(SCN)4

The low temperature electronic states of the organic conductors, α-(BEDT-TTF)₂MHg(SCN)₄ [M = K, Rb], have been studied by -NMR¹³C-NMR with the use of ¹³C labeled samples. We observed anomalies in the nuclear spin-lattice relaxatin rate, T₁, and shift of the NMR line below 8 K for the K salt and below 12 K for the Rb salt. These indicate some phase transition. However, absence of critical fluctuation near the transition temperature and absense of splitting or broadening of the NMR line is against the static magnetic ordering as found in usual SDW systems such as the TMTSF compounds. The present results imply that the electronic density of states decreases to a half below the transition.     

DISACCOMMODATION OF INITIAL SUSCEPTIBILITY IN AMORPHOUS Fe_(90-x)Ni_xZr_(10) ALLOYS

The disaccommodation(DA)measurements of initial susceptibility were performed inamorphous Fe_(90-x)Ni_xZr_(10)(x=10,20,30)alloys.The DA was measured for two differentamorphous states:as-quenched and pretreated at 537 K for 45 min.For all the as-quenched samples,in the isochronal spectra of DA a well defined relaxation peak around350 K is accompanied by a samll but distinct peak near the Curie temperature ofFe_(90)Zr_(10) phase(T_c=230 K).The reversibility and annealing effect on DA are analyzedwithin the framework of two-level model.The fits of the theory to the experimentaldata of reversible relaxation processes gave a spectrum,of activation energies and pre-exponential factor.     

非晶态Fe90—xNixZr10合金的起始磁化率减落

测量了非晶态Fe_(90-x)Ni_xZr_(10)(x=10,20,30)合金淬态和预处理态(573K,45min)样品的起始磁化率等时减落谱和等温减落谱,在等时减落谱的低温区(T<300K)观察到一伴随小峰,本文用二能级模型分析了弛豫过程的可逆性和热处理效应,对可逆减落谱的理论拟合给出可逆弛豫过程的激活能谱P(Q)和特征弛豫时间τ_(OR)。     

Crystal structure,ESR and conductivity studies of bis(ethylenedithio)tetrathiafulvalene (ET) organic conductor (H8-ET)2[Hg(SCN)2Br] and its deuterated analogue (D8-ET)2[Hg(SCN)2Br]

Protonated (I) and deuterated (II) crystals of (ET)₂[Hg(SCN)₂Br] (ET = bis(ethylenedithio)tetrathiafulvalene) are isostructural with B2/b space group and Z = 4. Crystal structure consists of (ET)₂⁺ dimers forming a κ-type motif and arranged in layers parallel to the bc-plane which are separated by anionic sheets of polymeric anions. A two-positional disorder exists in ethylene groups of deuterated ET molecules, while such disorder appears only in one of the ethylene groups in the hydrogenated salt. The crystals exhibit semimetallic behaviour at high temperatures with a transition to non-metallic state at 100 K for salt I and 60 K for salt II as is shown from d.c. conductivity measurements. Electron spin resonance (ESR) g factor and linewidth and their temperature behaviour are extensively discussed on the basis of existing theories and experimental data for low-dimensional organic conductors. The linewidth is determined by spin-phonon scattering driven relaxation processes which are mediated by Peierls fluctuations in the conducting phase and by spin-lattice relaxation processes below the critical temperature. The first-order phase transition in hydrogenated salt at 100 K is associated with a localization of electrons on ET dimers, whereas the transition of semiconductor-semiconductor type with possible magnetic ordering is suggested for deuterated salt. A considerable isotope effect in (ET)₂[Hg(SCN)₂Br] is considered to be related to a weak hydrogen bond between the terminal ethylene group of ET^dot;+ and the bromine atom of the anion in hydrogenated salt. A discussion of the nature of the phase transitions is given.     

压力对La-Al-(Cu,Ni)金属玻璃结构驰豫的影响

采用铜模吸铸法制备出La62.0Al15.7(Cu0.5Ni0.5)22.3大块金属玻璃,经高压处理后,用X射线衍射仪(XRD)和示差扫描量热计(DSC)对非晶的结构驰豫和晶化过程进行了研究.结果表明,非晶玻璃转变温度和第一晶化温度随着压力的增加,其先增加后减小,极大值出现在4.0 GPa的压力.这种现象归因于经过高压处理后玻璃转变温度区焓的变化,而焓的变化由基体缺陷激活体积引起自由体积变化所导致.此外,高压处理还影响玻璃的结晶过程.     

Magnetic property of the low temperature phase of α-(BEDT-TTF)2KHg(SCN)4

The low temperature phase of the organic conductor, α-(BEDT-TTF)₂KHg(SCN)₄, has been investigated by EPR measurements. The spin susceptibility determined by the EPR intensity is 3 × 10⁻⁴ emu/mol at room temperature, in agreement with the static susceptibility measurement. It decreases slightly with decreasing temperature down to 10 K, below which a rapid drop of the intensity is observed for all directions of the applied field. This temperature is close to the one which the resistivity anomaly was observed at. At temperatures below 20 K, the EPR signal was found to split into two or three lines depending on the external field direction. We discuss the possible origin of the splitting.     

Magnetic and transport properties of YbRhIn and YbPdIn

Electrical resistivity, magnetization and specific heat have been measured on a single crystal of YbRhIn and polycrystals of LuRhIn and YbPdIn. It is confirmed that YbPdIn is a metal with a divalent Yb ion. For YbRhIn, the electrical resistivity increases with logarithmic temperature dependence with decreasing temperature and saturates at a constant value below 20 K, while that of the nonmagnetic reference LuRhIn shows typical metallic behavior. The magnetic susceptibility of YbRhIn indicates that the Yb ion is in the trivalent state. The irreversibility of the magnetization curves which is observed in the high pulsed magnetic field below 1.5 K suggests an increase of relaxation time in the magnetic system. The specific heat increases rapidly below 4 K with decreasing temperature down to 0.9 K and moves toward higher temperatures on application of a magnetic field. These facts suggest that some magnetic transition to either ferromagnetic or spin-glass state occurs at low temperature.     

Thermally induced transitions of polarons to bipolarons in poly(3-dodecylthiophene)

The influence of thermal activation on polaron interactions of poly(3-dodecylthiophene) (PDDT) was studied. It was found that when an undoped PDDT sample was heated above 450 K and subsequently cooled to under the glass transition temperature, there were strong spin–spin interactions. When the polaron concentration was increased by FeCl₃ doping, all polarons including the immobile ones started to interact mutually. Changes in its internal microstructure, caused by thermal activation of the sample, followed by its freezing can generate an amplification of polaron interactions, giving rise to diamagnetic inter- and intra-chain bipolarons. As a result of strong spin–spin interactions the doped polymeric sample of PDDT displays diamagnetism even at room temperature. The diamagnetic properties depend on the consecutive structural relaxation of PDDT, caused either by immediate temperature changes, or by long-term standing at room temperature.     

结构弛豫对Zr_(64.13)Cu_(15.75)Ni_(10.12)Al_(10)块体非晶合金硬度和剪切带特征的影响

通过接近玻璃转变温度的等温退火获得不同弛豫状态的Zr64.13Cu15.75Ni10.12Al10块体非晶合金样品。利用维氏显微硬度计和洛氏硬度计研究结构弛豫对合金硬度和压痕周围剪切带特征的影响规律。结果表明:在590K等温退火处理使Zr64.13Cu15.75Ni10.12Al10块体非晶合金发生焓弛豫行为,其维氏显微硬度随退火时间的延长较快增加后趋于稳定,而大载荷洛氏硬度对结构弛豫不敏感。通过洛氏压痕周围剪切带特征的研究,定量比较了结构弛豫对剪切带间距、数量的影响规律。     

Nuclear magnetic resonance study of the electronic structure and hydrogen motion in the random b.c.c.-TaV2-H(D) system

Nuclear magnetic resonance measurements of the ¹H, ²D and ⁵¹V spin-lattice relaxation times and Knight shifts in the random b.c.c.-TaV₂H_x(D_x) system (0.1 x 2.4) have been performed over the temperature range 11–440 K. The relaxation data are analysed to obtain the parameters of H(D) diffusion, which is governed by a distribution of activation energies. The long-range diffusion of H(D) in b.c.c.-TaV₂H_x(D_x) is found to be much faster than in C15-type TaV₂H_x(D_x) with comparable H(D) contents. For all the studied samples (including those with mixed isotope composition) there is a distinct isotope effect on the average activation energy: . The measured values of the Knight shifts and the electronic (Korringa) contributions to the spin-lattice relaxation rates indicate that the density of d-electron states at the Fermi level decreases with increasing H(D) content.     

Relaxation of rapidly quenched metallic glasses: Effect of the relaxation state on the slow low temperature dynamics

The relaxation spectrum of rapidly quenched Mg₆₅Cu₂₅Y₁₀ metallic glass ribbons is studied by mechanical spectroscopy at temperatures below and around the glass transition. The comparison between hyper-quenched and relaxed samples is used to examine the origin of the low temperature “excess wing” of internal friction commonly observed in mechanical spectroscopy of metallic glasses. The results show that the excess wing can be attributed to access of the system to the broad α-relaxation process while evidence of secondary relaxations is not found. This suggests that in this glassy system the activation energies of structural relaxation and low temperature deformation are directly related to the activation energy of the main relaxation process of the glassy state.