Low temperature specific heat of (TTF) (TCNQ)

Low temperature specific heat measurements on (TTF) (TCNQ) are reported. The Debye temperature is 89.5 K. No term linear in temperature is observed, and comparison with other data indicates the low temperature phase is that of a small band gap non-magnetic semiconductor.     

Low temperature specific heat of 12442-type KCa2Fe4As4F2 single crystals

The Hubble constant H_0 represents the expansion rate of the Universe at present and is closely related to the age of the Universe.The accurate measurement of Hubble constant is crucial for modern cosmology.However,different cosmological observations give diverse values of Hubble constant in literature.Up to now,there are two methods to measure the Hubble constant.One is to directly measure the Hubble constant based on distance ladder estimates of Cepheids and so on.The other is to globally fit the Hubble constant under the assumption of a cosmological model,for example the "standard" ACDM model.Adopting the low-redshift observational datasets,including the Pantheon sample of Type Ⅰa supernovae,baryon acoustic oscillation measurements,and the tomographic Alcock-Paczynski method,we determine the Hubble constant to be 67.95_(-1.03)~(+0.78),69.81_(-2.70)~(+2.22) and66.75_(-4.23)~(+3.42) km s~(-1) Mpc~(-1) at 68% confidence level in the △CDM,wCDM and W_0W_a CDM models,respectively.Compared to the Hubble constant given by Riess et al.in 2019,we conclude that the new physics beyond the standard △CDM model is needed if all of these datasets are reliable.     

Low temperature specific heat in BaFe_(1.9)Ni_(0.1)As_2 single crystals

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.     

Low temperature specific heat of ErAs

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 $\text{S′ =}\text{3}\text{2}$ ground state.     

关于二硼化镁超导体比热的一点探索

在双带密度泛函理论的基础上,研究了双能隙超导体MgB2的超导态的比热跃变ΔC(T)与能隙的关系,指出了比热跃变的主要原因,并在转变温度Tc时将ΔC(T)/Tc的理论计算值与实验值作了对比,结果符合得很好。     

Low temperature specific heat of Cr-Fe-Si alloys

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.     

Low temperature specific heat of transition metals and alloys

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.     

Low temperature specific heat of Ni-Co and Ni-Fe alloys

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 data^5–7 and with theory: Gomes' model⁴ of a d-d tight-binding scattering in the dilute case, Hasegawa's^12,13 CPA calculations are both consistent with experiments.     

Low temperature specific heat of diethyl-morpholinium ditetracyanoquino-dimethane [DEM (TCNQ)2]

Specific heat measurements are reported for 0.5 K<T<50 K. Anomalous effects are observed near T = 30 K, which possibly can be attributed to a spin-Peierls transition. At low temperatures the specific heat contains a term linear in T indicating that one half of the TCNQ stacks is still in its unpertubed state.     

MgB2超导体能隙与比热的关系

基于双带模型,通过引入非电子—声子相互作用并利用自洽近似方法在BCS理论框架内讨论了硼化镁超导体的能隙及电子比热。     

Low temperature specific heat of single-domain and polydomain ferroelectric NaNO2

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.     

Ni-Zr amorphous alloys: Low temperature specific heat and superconductivity

The specific heat (C_p) of the amorphous alloys Ni_100-xZr_x for x = 75, 65, 55 and 35 was measured from 0.8K to 40K and the composition trends of the transition temperature T_c, the enhanced density of states at the Fermi level N_γ(_F) and the Debye temperatures θ_D(0), θ_D(T) established. For the three superconducting compositions (x=75, 65, 55) N_γ(E_F 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 $\text{N}{}_0\text{(E}{}_{\mathrm{F}}\text{) =}\text{N}{}_{\mathrm{\gamma }}\text{(E}{}_{\mathrm{F}}\text{)}\text{(1 + λ}{}_{\mathrm{p}}\text{)}$ 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.     

Low temperature heat capacity of TTF (TCNQ)

Low temperature heat capacity measurements of two TTF (TCNQ) polycrystalline samples are reported. The existence of a linear term and an anomolously high Debye temperature for one of them at low temperatures are attributed to impurity effects. The literature data on other (TCNQ) salts are discussed.     

Low temperature specific heat of KCl: OH with high OH concentration

We report on measurements of the specific heat (between 0.035 and 3 K) of two KCl crystals doped with 0.5 and 1 at.% OH^-. For the 1 at.% sample, the excess specific heat C due to OH^- varies roughly linearly between 0.035 and 0.6 K. A similar behaviour is also found for 0.5 at.% between 0.2 and 0.6 K while below 0.2 K, C ～ T^1.8. Thus, contrary to previous measurements, a T^{$\text{3}\text{2}$} dependence is not observed. We discuss our results in terms of strain and electric dipolar interactions.     

Order parameter anisotropy of MgB2 using specific heat jump of layered superconductors

The recently obtained analytical result [1] for renormalization of the jump of the heat capacity (C _S–C _N)/C_N by anisotropy of the order parameter is applied to the layered superconductors. The graph of (C _S–C _N)/C _N vs. the anisotropy of the order parameter allows a direct determination of the gap anisotropy in MgB₂ using available experimental data     

Low temperature specific heat of Cu3Au

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.     

Electronic specific heat and high field magnetization studies on the Y6(Fe1−xMnx)23 system

Magnetizations at applied fields up to 120 kOe and electronic specific heats have been determined for ternaries represented by the formula Y₆(Fe_1?xMn_x)₂₃. The Curie temperature and ordered magnetic moment of Y6Mn₂₃ and Y₆Fe₂₃ decrease sharply when these materials are formed into solid solutions, being minimal in the vicinity of the equimolal solution. To test whether the reduction is a band effect electronic specific heats were measured; they are maximal where T_c and the moment are minimal, indicating unimportance of band effects. Curie-Weiss behavior is exhibited at low fields, suggesting rather localized d-electrons. The nearest neighbor distances are such as to lead to antiferromagnetic Mn-Mn interactions. Y₆Mn₂₃ is taken to be ferrimagnetic whereas Y₆Fe₂₃ appears to be ferromagnetic. While the magnetic structure of the ternaries is yet to be fully clarified, it is clear that antiferromagnetic exchange is enhanced when either binary is formed into a ternary. It also appears that the Mn-Fe coupling is antiferromagnetic in the ternaries.