Here we present the results of the zero-field specific heat study of the LuFe_6Al_6 single crystal. The specific heat data were analyzed as a sum of the phonon, electronic, and magnetic contributions, respectively. The analysis of the phonon part involves three acoustic and 36 optical branches, respectively, all of them corrected for the anharmonicity. The magnetic part of the specific heat was obtained by subtracting the electronic and the phonon part from the experimental specific heat and the magnetic entropy was calculated.
Heat capacity measurements performed on the new ternary compound YbCu_4Ni indicate for this compound strong electronic correlations with possible antiferromagnetic phase transition below 0.5 K. Susceptibility and magnetisation measurements above 2 K show no magnetic ordering.
Measurements of the heat capacity in ultralow temperatures (down to 350 mK) have been carried out for Ce_{1-x}La_{x}NiAl_4. The paramagnetic behavior above about 30 K can be well described by the Curie-Weiss magnetic susceptibility. The undoped CeNiAl_4 compound is a known heavy fermion system with a large electronic specific heat coefficient (γ = 0.5 J mol^{-1} K^{-2}) and the Kondo temperature in the range 30-80 K. In the case of the Ce_{0.8}La_{0.2}NiAl_4 and Ce_{0.6}La_{0.4}NiAl_4 compounds a peak in C/T appears below 2 K, which is strongly damped by the magnetic field. It is probably connected with the Kondo and/or magnetic interactions and the electronic specific heat coefficient is 0.19 J mol^{-1} K^{-2} (0.43 J mol^{-1} K^{-2}) for x = 0.2 (x = 0.4) at T → 0. The value determined above the peak, at temperature for which the magnetic field starts to decrease γ ( ≈ 3 K), is about 0.5 J mol^{-1} K^{-2} and the effect of the magnetic field can be well analyzed in frames of the single-ion Kondo model.
The thermal conductivity of CsGd(MoO_4)_2 has been studied in the temperature range from 2 to 50 K in zero magnetic field. The analysis of the data performed within the Debye model with the relaxation-time approximation revealed the presence of the scattering of phonons by critical fluctuations. The behaviour of phonon mean free path at the lowest temperatures is discussed.
Electrical resistance, transversal magnetoresistance and the Hall effect were studied on polycrystalline CaTi_xRu_{1-x}O_3 (x=0, 0.07) samples using a conventional Quantum Design PPMS-9 equipment in the temperature range 2-300 K and magnetic field up to 9 T. Substantial differences were found between the two samples: (i) opposite to the metallic character of CaRuO_3, the substituted sample has insulating-like electrical resistance;(ii) the magnetoresistance of the substituted sample changes the sign from negative to positive values with increasing temperature. The magnetoresistance of CaRuO_3 is negative, the sign reversal is induced by magnetic field and only at temperatures below 15 K, such a behaviour is predicted for clustered systems;(iii) the Hall voltage in pure CaRuO_3 also changes sign from negative to positive values above 35 K. This temperature coincides with the observed magnetic transition temperature, indicating that the magnetic state and the carrier character interrelate.
The influence of Ti substitution on the specific heat of the CaTi_xRu_{1-x}O_3 system at low concentrations x=0, 0.005, and 0.03 was studied in the temperature range of 2-300 K at magnetic fields up to 9 T. Small peak was revealed in the C/T vs. T^2 dependence at around 3 K, which are field sensitive (the electronic specific heat coefficient γlinearly decreases with the increase in magnetic field), and might be connected to some kind of magnetic ordering. The coefficient γis suppressed also by Ti substitution.
In the presented work we report electrical, magnetic and thermal properties of EuB_{6-x}C_{x} single crystals with an estimated value of x ≈ 0.07. Our studies reveal an antiferromagnetic phase transition at T_{N} ≈ 6.7 K. Electrical resistivity at zero magnetic field shows a pronounced resistivity maximum at T_{M} ≈ 7 K, just above the antiferromagnetic phase transition temperature. With increasing applied magnetic field the maximum moves to lower temperature and becomes totally suppressed at the field of 9 T. Observed magnetoresistance is negative in the whole studied temperature range 2-20 K, yielding a ratio of ρ(0 T, 7 K)/ρ(9 T, 7 K) ≈ 2.5. The origin of such magnetoresistance is associated with formation of mixed magnetic structure in the system due to fluctuation of carbon concentration.
The heat capacity in the applied magnetic field up to 9 T, susceptibility and magnetization of polycrystalline CeCu_4Al are presented. The determined electronic heat capacity coefficient γ= 210 mJ mol^{-1} K^{-2} confirmed heavy fermion character of this compound. Magnetic ordering was not observed down to 0.5 K. Magnetic properties confirm these observations.
Results of thermal conductivity measurements on single crystalline PrB_6 sample in the temperature range of 2-30 K and in magnetic field up to 14 T are presented. The obtained results are discussed in order to estimate the electron, phonon, and magnetic contributions to thermal conductivity. Taking into account the results of electrical resistivity of this compound the temperature dependence of the reduced Lorentz function is determined.
A series od UFe_{2+x} materials was prepared using splat cooling. The Laves phase structure can accommodate up to 0.3 Fe excess, while T_C is enhanced from 172 K to approximately 240 K. Higher Fe concentration leads to the segregation of α-Fe. ^{57}Fe Mössbauer spectroscopy indicates higher Fe magnetic hyperfine fields on Fe nuclei occupying the U sublattice than for the regular Fe sites.
We present a comparative study of Na_{0.7}CoO_2 samples obtained from three different sources and prepared by different methods. The specific heat and magnetic susceptibility measurements in the temperature range 2-300 K show substantial influence on the observed anomalies, which underlines that the system is extremely sensitive to preparation protocols.
The thermal conductivity of the quasi-one-dimensional S = 5/2 Heisenberg antiferromagnet CsMnCl_3·2H_2O with the intrachain interaction J/k_{B} = 3 K was experimentally studied at temperatures from 2 to 25 K. The data analysis performed within the Debye model with the relaxation-time approximation unambiguously indicates the presence of the scattering of phonons on magnetic subsystem.
The studies of the electronic structure and the specific heat of YNi_4Si are reported. Below the Fermi energy (E_F) the density of states contains mainly the 3d states of Ni, which hybridized with 4d states of Y and 3p states of Si. The theoretical electronic specific heat coefficient (12.32 mJ/(mol K^2)) obtained for equilibrium lattice parameters and the experimental value (13 mJ/(mol K^2)) are in a reasonable agreement.
JavaScript is turned off in your web browser. Turn it on to take full advantage of this site, then refresh the page.