共查询到19条相似文献,搜索用时 112 毫秒
1.
2.
3.
4.
5.
对电脉冲诱导的不同电阻态下La0.7Ca0.3MnO3样品的比热进行了研究.实验结果表明,电脉冲导致La0.7Ca0.3MnO3样品比热随电阻状态发生可逆变化.比热随电阻状态的减小而减小.低温比热拟合及不同电阻状态下的比热差与温度关系说明,声子对比热的贡献不随电阻状态变化,磁性和载流子对比热的贡献是导致La0.7Ca0.3MnO3样品比热变化的原因.电脉冲诱导O离子沿一维扩展性缺陷的电化学迁移,导致材料中局部区域的O离子浓度发生变化.O离子浓度的变化导致载流子浓度的变化,同时载流子浓度的变化将使得低温下磁性耦合强度发生变化,从而导致比热发生变化.
关键词:
0.7Ca0.3MnO3')" href="#">La0.7Ca0.3MnO3
比热
氧离子迁移 相似文献
6.
7.
8.
用铜模吸铸法获得了直径为5mm的一种新的Pr基大块非晶.与以往其他稀土-过渡金属(RE-TM)大块非晶不同的是,这种新的Pr基大块非晶具有明显的玻璃转变和稳定的过冷液相区,且其玻璃转变温度在目前已知的大块非晶中是最低的,Tg=409K.研究了该大块非晶的玻璃转变动力学,并给出了Kauzmann温度Tk、Vogel-Fulcher温度T0g及脆性参数m等重要参数.
关键词:
大块非晶
玻璃转变
脆性参数m 相似文献
9.
测量了重电子金属CeCu6-xNix(x=0,005,01,015,02)01K—250K的低温电阻和5K—70K低温比热,发现样品电阻的极大值温度随着掺Ni含量的增大而急剧下降,这一现象反映少数与Ni邻近的Ce离子在极低温下磁矩的加强和整个Ce离子点阵对导电电子相干散射的减弱.与此相反,低温电子比热系数γ在较低温度下近于常数,而在8K附近因有效质量变大而明显上升,但γ明显上升的温度,对Ni的含量却不敏感,表明绝大部分Ce离子的状况并未受到影响
关键词:
重费米子系统
低温比热
低温电阻 相似文献
10.
11.
G. Kh. Panova M. N. Khlopkin N. A. Chernoplekov A. A. Shikov 《Physics of the Solid State》2002,44(7):1218-1223
The specific heats of the Ni2B amorphous system and of its crystal analog were studied in the temperature range 3–270 K. The data obtained permitted us to isolate the contribution due to atomic vibrations from the experimentally measured specific heat, determine the electronic density of states at the Fermi level and the temperature dependence of the characteristic Debye parameter Θ, and to calculate some average frequencies (moments) of the vibrational spectrum. The electronic density of states at the Fermi level increases under amorphization. An analysis of the temperature dependence of the lattice specific heat showed that amorphization brings about a substantial growth in the density of vibrational states at low frequencies, whereas the spectrum-averaged and rms frequencies change very little, which is in good agreement with neutron diffraction measurements. 相似文献
12.
The low-temperature specific heat of freshly prepared and annealed amorphous alloys Zr70Be30, Zr67Cu33, and Zr75Rh25 has been investigated experimentally. The integral parameters of the electronic and phonon spectra have been determined:
the Sommerfeld coefficients and the Debye temperatures. Data from calorimetric and neutron experiments were compared on the
basis of the theory of lattices with off-diagonal disorder and localized modes. It is concluded that a local rearrangement
of the structure occurs in freshly prepared samples as the temperature decreases. A model of a bistable impurity configuration
is proposed to explain this restructuring.
Fiz. Tverd. Tela (St. Petersburg) 39, 145–152 (January 1997) 相似文献
13.
Transport and specific heat properties have been studied on the orthorhombic molybdenum oxide γ-Mo4011. The anisotropy of the electrical resistivity establishes that this compound is a quasi two-dimensional metal, as expected from crystal structure data. Both the resistivity and the thermopower show that an electronic transition, probably due to a charge density wave instability takes place at Tc = 100 K. Low temperature specific heat data provide an estimation of the Debye temperature and of the electronic density of states in the low temperature metallic phase. 相似文献
14.
Awadhesh Mani J. Janaki Soubhadra Sen A. Bharathi Y. Hariharan 《Solid State Communications》2008,146(9-10):391-394
The temperature dependent specific heat studies of a Ru substituted Fe1−xRuxSi Kondo Insulating system has been carried out in the 77 to 300 K range. The specific heat has been analyzed based on contributions from an electronic part and a lattice part. For the electronic part a Gaussian density of states model, which incorporates the effect of correlation, band structure and disorder in its defining parameters is used. The lattice part of specific heat is described in the Debye model. Parameters that define the electronic density of states and the Debye temperature are extracted from fits of the temperature dependent specific heat data and are compared with earlier resistivity measurements that employed a similar analysis. 相似文献
15.
The specific heat and magnetic susceptibility of the transition metal oxide ReO3 have been measured. The specific heat results give a Debye temperature ΘD = 460 ± 10 K and an electronic specific heat coefficient γ = 6.45 ± 0.07 cal/mole K2 which are in good agreement with similar measurements on the cubic sodium tungsten bronzes. The magnetic susceptibility and the electronic contribution to the specific heat are within a few percent of the corresponding parameters calculated from the free electron model with one electron per unit cell. Our results show that ReO3 behaves much like a simple metal. No experimental evidence for narrow d-band effects was observed. 相似文献
16.
The low-temperature specific heat (LTSH) of the melt-quenched Ni81.5Px- B18.5?x amorphous alloy system, with 0 ? x ? 18.5, is presented. The decomposition of the LTSH into magnetic, lattice and electronic contributions shows that both Debye temperature θD and electronic specific heat coefficient decrease when the concentration of P increases.The electronic density of states N(EF), deduced from γ for various Ni-metalloid alloys, is plotted as a function of the average electronic concentration xZM, where x is the metalloid concentration and ZM is the chemical valence of M. Following Malozemoff et al.'s work, this plot is considered as a representation of the band structure and yields the change of the Fermi level with alloying. 相似文献
17.
R. Lagnier C. Ayache J.-Y. Harbec S. Jandl J.-P. Jay-Gerin 《Solid State Communications》1983,48(1):65-68
The specific heat of the layer compound semiconductor tin diselenide SnSe2 has been measured in the temperature range from 2.7 to 280 K. In this range, the overall temperature dependence of the specific heat is dominated by the lattice contribution, which yields a limiting Debye characteristic temperature at absolute zero θD (0) = 140 ± 2K. The increase in the specific heat at low temperatures is more gradual than what would be expected for a simple Debye solid, and reflects the quasi-two dimensional layer structure of this compound. 相似文献
18.
G. Kh. Panova G. F. Syrykh M. N. Khlopkin A. A. Shikov 《Physics of the Solid State》2003,45(4):605-609
The specific heats of the amorphous systems Ni44Nb56, Ni62Nb38, and Cu33Zr67 were studied in the temperature range 3–273 K. The data obtained allow one to isolate the contribution due to atomic vibrations from the experimentally measured specific heat, to determine the density of electronic states at the Fermi level and the temperature dependence of the characteristic Debye parameter Θ over a broad temperature range, and to calculate a few frequency moments that characterize the vibrational spectrum. The information derived on the average characteristics of vibrational spectra is in good agreement with earlier data on inelastic neutron scattering. In transferring from Ni44Nb56 to Ni62Nb38, the density of electronic states at the Fermi level decreases and the characteristic vibrational frequencies increase. The density of electronic states at the Fermi level for Cu33Zr67 is close to that for Ni62Nb38. The characteristic frequencies of the vibrational spectrum of the Cu33Zr67 system are substantially lower (by 30%) than those of the Ni44Nb56 and Ni62Nb38 systems. 相似文献
19.
利用基于密度泛函理论的第一性原理平面波赝势方法 并结合准谐徳拜模型研究了NaCl结构的TiC在高压下的弹性性质、电子结构和热力学性质. 计算所得零温零压下的晶格常数、体弹模量及弹性常数与实验值符合得很好. 零温下弹性常数和弹性模量随压强增大而增大. 通过态密度和电荷密度的分析, Ti-C键随压强增大而增强. 运用准谐德拜模型, 成功计算了TiC在高温高压下的体弹模量、熵、热膨胀系数、徳拜温度、 Grüneisen参数和比热容. 结果表明压强对体弹模量、热膨胀系数和徳拜温度的影响大于温度对其的影响. 热容随着压强升高而减小, 在高温高压下, 热容接近Dulong-Petit极限. 相似文献