共查询到20条相似文献,搜索用时 15 毫秒
1.
《中国科学:物理学 力学 天文学(英文版)》2020,(9)
Low-temperature specific heat(SH) is measured for the 12442-type KCa_2Fe_4As_4F_2 single crystal under different magnetic fields.A clear SH jump with the height of ?C/T|_(T_c)= 130 mJ mol~(-1) K~(-2) is observed at the superconducting transition temperature T_c.It is found that the electronic SH coefficient ?γ(H) quickly increases when the field is in the low-field region below 3T and then considerably slows down the increase with a further increase in the field, which indicates a rather strong anisotropy or multi-gap feature with a small minimum in the superconducting gap(s). The temperature-dependent SH data indicate the presence of the T~2 term, which supplies further information and supports the picture with a line-nodal gap structure. Moreover, the onset point of the SH transition remains almost unchanged under the field as high as 9 T, which is similar to that observed in cuprates, and places this system in the middle between the BCS limit and the Bose-Einstein condensation. 相似文献
2.
Teng Wang Chi Zhang LiangCai Xu JinHua Wang Shan Jiang ZengWei Zhu ZhaoSheng Wang JiaNan Chu JiaXin Feng LingLing Wang Wei Li Tao Hu XiaoSong Liu Gang Mu 《中国科学:物理学 力学 天文学(英文版)》2020,(2):124-129
Recently, 12442 system of Fe-based superconductors has attracted considerable attention owing to its unique double-Fe As-layer structure. A steep increase in the in-plane upper critical field with cooling has been observed near the superconducting transition temperature, Tc, in KCa2Fe4As4F2 single crystals. Herein, we report a high-field investigation on upper critical field of this material over a wide temperature range, and both out-of-plane(H∥c, Hc2c) and in-plane(H∥ab, Hc2ab ) directions have been measured.A sublinear temperature-dependent behavior is observed for the out-of-plane Hc2c , whereas strong convex curvature with cooling is observed for the in-plane Hc2ab . Such behaviors could not be described by the conventional Werthamer-Helfand-Hohenberg(WHH) model. The data analysis based on the WHH model by considering the spin aspects reveals a large Maki parameter α=9,indicating that the in-plane upper critical field is affected by a very strong Pauli paramagnetic effect. 相似文献
3.
《中国科学:物理学 力学 天文学(英文版)》2010,(7)
Low-temperature specific heat was measured on the BaFe1.9Ni0.1As2 single crystals with critical transition temperature Tc = 20.1 K.A clear specific heat jump with the value ΔC/T|Tc ≈ 23 mJ/mol K2 was observed.In addition,a roughly linear magnetic field dependence of the electronic specific heat coefficient Δγ(H) was found in the zero-temperature limit,suggesting that at least one Fermi pocket,probably the hole derivative one,was fully gapped with a small anisotropy in the present sample.A slight curvature of the curve Δγ(H) may suggest a complex gap structure(anisotropic gap or nodes) at other Fermi surfaces. 相似文献
4.
The specific heat of a sintered sample of ErAs has been measured from 1.4–6.1 K. A single broad κ-like peak in the data occurs at 3.25K. The entropy associated with the peak is approximately R ln4 suggesting an ground state. 相似文献
5.
Ashok Rao Bhasker Gahtori S.K. Agarwal Tirthankar Chakraborty Chandan Kumar Sarkar Anirban Das 《Physica C: Superconductivity and its Applications》2009,469(1):64-69
Polycrystalline samples of MgB2 superconductor (Mn-doped as well as pristine) were investigated by measurements of the electrical resistivity, magneto-resistance in the temperature range of 4–300 K. All the samples show metallic behaviour. It is observed that the upper critical field slightly decreases with Mn concentration. Specific heat measurements were performed with field as well as without field. For comparison, we also prepared one Fe-doped and specific heat measurements were also carried out on this sample. It is observed that the jump in specific heat decreases with increase in Mn content. 相似文献
6.
Low temperature specific heats of Cr-Fe-Si alloys with 3 at. % Si were investigated between 1.4°–4.2°K. The electronic specific heat coefficient γ essentially varies with transition metal electron concentration ( e/a) in the same manner as the Cr-Fe alloys but with the high γ peak slightly shifted to lower e/a. The shift of γ peak suggests transfer of electrons from Si atoms to the 3d magnetic subband of the transition elements. 相似文献
7.
Magnetization measurements on TbAl2 single crystals are reported for 4.2 K in magnetic fields up to 50 kOe applied in the three symmetry directions. We find 〈111〉 as the easy and 〈100〉 as the hard direction of magnetization. No quenching of the magnetic moment is observed. The results are interpreted in terms of the crystalline electric field. 相似文献
8.
Xiang-Zhuo Xing Wei Zhou Chun-Qiang Xu Nan Zhou Fei-Fei Yuan Yu-Feng Zhang Xiao-Feng Xu Zhi-Xiang Shi 《Frontiers of Physics》2017,12(4):127401
The effects of isovalent Sb substitution on the superconducting properties of the Ca0.88La0.12Fe2(As1-ySby)2 system have been studied through electrical resistivity measurements. It is seen that the antiferromagnetic or structural transition is suppressed with Sb content, and a high-Tc superconducting phase, accompanied by a low-Tc phase, emerges at 0.02 ≤ y ≤ 0.06. In this intermediate-doping regime, normal-state transport shows non-Fermi-liquid-like behaviors with nearly T-linear resistivity above the high-Tc phase. With further Sb doping, this high-Tc phase abruptly vanishes for y > 0.06 and the conventional Fermi liquid is restored, while the low-Tc phase remains robust against Sb impurities. The coincidence of the high-Tc phase and non-Fermi liquid transport behaviors in the intermediate Sb-doping regime suggests that AFM fluctuations play an important role in the observed non-Fermi liquid behaviors, which may be intimately related to the unusual nonbulk high-Tc phase in this system. 相似文献
9.
《Solid State Communications》1986,59(12):855-860
The incorporation and charge of iron in ZnWO4:Fecrystals were investigated by absorption spectrometry. The UV bands at 350 nm and the visible band at 460 nm have been found to be related to Fe3+ and Fe2+ ions respectively. Both ions are mainly in substitutional Zn positions. The infrared absorption at 3445 cm−1 is related to Fe3+ OH complexes. The OH− ions compensating the excess charge of Fe3+ are probably situated in interstitial positions. 相似文献
10.
Values of the low temperature specific heat of f.c.c. Ni-Co and Ni-Fe alloys have been determined in the 1.2–8 K range with a relative accuracy of 10-3 and analysed to separate the electron, phonon, magnon and hyperfine terms. Results are in good agreement with former data5–7 and with theory: Gomes' model4 of a d-d tight-binding scattering in the dilute case, Hasegawa's12,13 CPA calculations are both consistent with experiments. 相似文献
11.
The article reviews experimental results on the low temperature specific heat of the transition metals and their alloys. Particularly discussed are the variations of the electronic part on the basis of a complete compilation of measurements given. 相似文献
12.
13.
Contrary to a recent letter of Gavignet-Tillard and Hammann, it has been shown that ordering does have a significant effect on the electronic specific heat of Cu3Au. 相似文献
14.
The splitting of the anomaly revealed in the specific heat of real crystals of potassium dihydrogen phosphate KH2PO4 is discussed. It is demonstrated that the observed effect is characteristic of first-order phase transitions occurring near the tricritical point and originates from the specific features inherent in the defect structure of real crystals. A method is proposed for describing the experimentally observed splitting of the specific heat anomaly in the framework of the Landau theory with due regard for the possible formation of metastable states characterized by the polarization aligned antiparallel to the applied electric field in the polar phase. 相似文献
15.
The specific heat of a NaNO2 sample has been measured between 2 K and 40 K in both single-domain and polydomain states. In this region the specific heat of the single domain sample follows exactly the T3 dependence. A clear excess contribution which in this temperature range has a temperature dependence between T and T2 has been detected for the polydomain sample. It is attributed to domain walls. 相似文献
16.
We measured the temperature dependences of light reflection and transmission of bismuth germanate single crystals upon cyclic
variation of their temperature in the range of 94–340 K. We revealed an asymmetric temperature hysteresis of reflection, which
is accompanied by a change in the Rayleigh scattering. Heating of crystals, in contrast to their cooling, is accompanied by
a decrease in the reflection in the range of 100–287 K and near 310 K. We found that reflection minima in the first and second
temperature ranges arise as a result of the action of different mechanisms. We assume that temperature changes in the reflection
are related to structural phase transitions in the superficial layer. 相似文献
17.
Commercial computers based on electronic logic devices have brought great changes to the world. However, traditional electronic devices are suffering from numerous technical challenges in their attempts to continue to satisfy Moore's law. Alloptical logic devices, as promising successors to their electronic counterparts, have become a major focus of optics research. In this paper, we provide a review of current all-optical logic devices. The logic gates in these devices, which are described in the first part of the review, are divided into five categories based on the different principles used in their realization. Complex optical devices with various functions and reconfigurable devices are summarized in the next section. In the final part of this paper, we discuss some of the previous works on all-optical integrated chips with specific functions. This review will provide a complete technological roadmap for all-optical devices and aims to be helpful in possible future developments in this growing field. 相似文献
18.
The specific heat (Cp) of the amorphous alloys Ni100-xZrx for x = 75, 65, 55 and 35 was measured from 0.8K to 40K and the composition trends of the transition temperature Tc, the enhanced density of states at the Fermi level Nγ(F) and the Debye temperatures θD(0), θD(T) established. For the three superconducting compositions (x=75, 65, 55) Nγ(EF increases rapidly with increasing [Zr] in agreement with the trend in amorphous Cu-Zr alloys. However, for the Zr-Ni alloys the bare density of states increases strongly with [Zr] in contrast to the Zr-Cu alloys where it is reported to be almost constant. We conclude that for the Ni-Zr alloys the electron-ion matrix element <I2> decreases with increasing [Zr]. Other results are related to recent photoemission studies of these alloys. 相似文献
19.
Y. Nakajima Y. Tsuchiya T. Taen T. Tamegai H. Kitamura T. Murakami 《Physica C: Superconductivity and its Applications》2011,471(21-22):647-650
We report the suppression of the critical temperature Tc in single crystalline Ba(Fe1?xCox)2As2 at under-, optimal-, and over-doping levels by 3 MeV proton irradiation. Tc decreases and residual resistivity increases monotonically with increasing the dose. The low-temperature resistivity does not show the upturn in contrast with the α-particle irradiated NdFeAs(O,F), which suggests that proton irradiation introduces nonmagnetic scattering centers. Critical scattering rates for all samples obtained by three different ways are much higher than that expected in s±-pairing scenario based on inter-band scattering due to antiferro-magnetic spin fluctuations. 相似文献