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1.
Investigations of the pressure dependence of the superconducting transition temperature Tc up to 17 kbar, and of the normal conductivity up to 50 kbar are reported. It is observed that below 8 kbar, the value of Tc increases linearly with the pressure. In addition, there is a significant drop of Tc at about 9 kbar which may be due to a phase transition.  相似文献   

2.
Magnetization measurements have been carried out under hydrostatic pressures up to 6 kbar and constant magnetic fields (10 kOe) in CsCl-type compounds: CeMg and CeZn. a decrease in the Néel temperature, TN, with increasing pressure is observed in both compounds (dTN/dp=- 0.2 and -0.17 K kbar-1 respectively in CeMg and CeZn). The relative decrease of TN has a similar order of magnitude to that found in other cerium compounds with Kondo-type properties.  相似文献   

3.
The pressure derivative of the Curie temperature dTc/dp of the Heusler alloys Ni2MnZ(Z = Al, Ga, In, Sn and Sb) has been obtained from the results of temperature dependence of initial permeability under pressure up to about 6 kbar. For all alloys the Curie temperatures increase linearly with increasing pressure at the rate of dTc/dp: +0.7 K/kbar for Ni2MnAl, +1.0 K/kbar for Ni2MnGa, +0.9 K/kbar for Ni2MnIn, +1.4 K/kbar for Ni2MnSn and +4.1 K/kbar for Ni2MnSb. On the basis of these results, the interatomic dependence of the exchange interaction for Heusler alloys is discussed. The magnetic susceptibilities of those alloys are also reported.  相似文献   

4.
A Mössbauer measurement of the pressure dependence of the Néel temperature in FeF2 is reported. Up to the maximum pressure of 50 kbar TN increases at the rate of 0.27 ± 0.03°K/kbar. When this pressure dependence is converted to volume dependence, the result, d In TN/d In V = 3.2 ± 0.3, is found to obey the “103 rule” established by Bloch for a wide variety of antiferromagnetic insulators.  相似文献   

5.
The dependence of the Verwey temperature Tv on the uniaxial pressure P was determined. It was found that along the [111] axis dTv/dP ≈ 10K/kbar while along the [110] and the [001] axes, dTv/dP ≈ 1 K/kbar. The results emphasize the important role played by the rhombohedral distortion in the Verwey transition.  相似文献   

6.
The electrical resistivity of α-Mn was measured from 4.2 K to 290 K at pressures up to 8 kbar. The residual resistivity was found not to depend on pressure. The Néel temperature decreases linearly with pressure at a slope dTN/dP = − 1.7 ± 0.2 K/kbar.  相似文献   

7.
Polycrystalline samples of electron-doped Pr1.85Ce0.15CuO4+δ have been prepared under different annealing conditions and investigated by means of X-ray-diffraction, oxygen content analysis, electrical resistivity, magnetic susceptibility and low temperature specific heat measurements. X-ray-diffraction patterns show that samples contain a single T′ phase. The superconducting transition temperatures Tcm taken with the onset of diamagnetism in magnetic-susceptibility measurements are 20 and 19.5 K for sample annealed in flowing Ar gas and in vacuum (∼10−3 torr), respectively. The data of the samples, which are annealed in flowing Ar gas, show clear evidence for an αT2 term at zero magnetic field in superconducting electronic specific heat, and are consistent with d-wave superconductivity. However, this behavior is not observed in the other sample, which is annealed in vacuum. These results indicate that different heat treatments affect the oxygen content, homogeneity, superconducting transition temperature Tc, superconducting volume fraction, and the superconducting pairing symmetry of Pr1.85Ce0.15CuO4+δ.  相似文献   

8.
We have studied the pressure dependence of the superconducting transition temperature of amorphous (Mo0.6Ru0.4)86B14 for hydrostatic pressures up to P ~ 9 kbar. The transition temperature Tc decreases with pressure at a rate dTc/dP=-(9±1) mK kbar-1. We estimate the Grüneisen parameter and the volume dependence of the electron-phonon coupling constant.  相似文献   

9.
The temperature dependence of the electrical conductivity of magnetite was measured under hydrostatic pressure up to 18.4 kbar. It is found that the temperature of the conductivity maximum in the high temperature phase is more rapidly reduced by pressure (dTm/dP = -4.1 K/kbar) than the Verwey temperature (dTv/dP = -0.27 K/kbar). The discontinuous change of the conductivity at Tv appears to increase with applied pressure as a result of a lowering of Tm.  相似文献   

10.
The electrical resistivity of LaAg has been measured from 1–300 K at hydrostatic pressures to 12.4 kbar and the superconducting transition temperature Tc determined inductively to 23 kbar. For P ? 6.2 kbar a lattice transformation is observed at a temperature TM which increases rapidly with pressure. Tc shows an oscillatory pressure dependence, increasing initially from Tc (0) = 1.062 K. There is no obvious correlation between the pressure dependence of TM and Tc.  相似文献   

11.
《Physics letters. A》1988,134(3):196-198
The pressure effect on the Curie temperature Tc of CoCr2O4 was measured under pressures up to 11.5 kbar. The pressure derivative of Tc is found to be +0.25 K/kbar. On the basis of this result, the relationship between the magnetic transition temperature and volume is discussed.  相似文献   

12.
We have measured the resistivity of NbSe3 doped with 5% Ta from room temperature down to 0.5K and compared our results with similar measurements on pure NbSe3. The pure sample remains normal to the lowest temperature (0.5K), whereas the doped sample has a sharp transition to the superconducting state with Tc = 1.5 ± 0.2 K. Measurements of the critical magnetic field indicate that the Ta doped samples are homogeneous, anisotropic three dimensional superconductors.  相似文献   

13.
《Physics letters. A》1987,126(2):130-132
The superconducting transition temperature Tc, detected by the Meissner effect, of the single-phase (Y1.2Ba0.8)4Cu4 O16−δ ceramic compound has been studied under hydrostatic pressure up to 3.4 kbar. The Tc increases with the increase of pressure at a rate of 1.5 K/kbar. The observed pressure behaviour of Tc is discussed with reference to a crystal structure and a cooperative bipolaron tunneling induced by Jahn-Teller distortions.  相似文献   

14.
We have analyzed the temperature and magnetic-field dependences of resistivity ρ(T, H) of semiconducting compound Pb0.45Sn0.55Te doped with 5 at % In under a hydrostatic compression at P < 12 kbar. It is found that the temperature dependence ρ(T) at all pressures at T < 100 K is exponential with the activation energy decreasing upon an increase in pressure; this is accompanied with a superconducting transition on the ρ(T) and ρ(H) dependences at P > 4.8 kbar at T > 1 K (T c = 1.72 K at a level of 0.5ρ N at P = 6.8 kbar). We consider the model describing the low-temperature “dielectrization” of the semiconducting solid solution and the formation of the superconducting state upon an increase in the hydrostatic compression P > 4 kbar.  相似文献   

15.
Both antiferromagnetic (TN) and weak ferromagnetic (Tc) transition temperatures of NiS2 have been measured under pressure up to 18.4 kbar. Values of dTN/dP=(0.9 ± 0.1) deg/kbar and dTc/dP=(0.4 ± 0.1) deg/kbar are obtained. The present results allow estimates of the magnetic Grüneisen constant γm = - d ln TN/d ln V of (26±5) and of the entropy change of (1.4±0.5) J/mol·deg at the first order transition temperature Tc.  相似文献   

16.
The superconducting transition temperature (Tc ≅ 36 K) of single-phase La1.85Sr0.15CO4 increases under hydrostatic pressure at the rapid rate +0.28 K/kbar (+0.78 %/kbar), whereas the Pauli susceptibility at 70 K changes by less than 0.2 %/kbar. This result provides evidence that in this compound the electronic density of states is not the predominant factor determining the anomalously high values of either Tc or its pressure derivative.  相似文献   

17.
The neutron diffraction experiment we have made on NiS1.91 single crystal under increasing pressure (0<P<30 kbar) indicates a constant increase of the Néel temperature of the sample. For high pressures (P>20 kbar) and low temperatures the sample is in an antiferromagnetic metallic state as suggested by theoretical considerations for a Mott-Hubbard insulator. The pressure dependence of the second magnetic transition in NiS2 (T = 31 K for P = 0) is also reported.  相似文献   

18.
Non-Fermi-liquid behavior and close proximity to a quantum critical point in the 5d transition metal iridate SrIrO3 at ambient pressure motivate our search for possible anomalous behavior in its transport properties under pressure. The electrical resistivity in the ab-plane of a single crystal of SrIrO3 has been measured over the temperature range 1.35–285 K at both ambient and 9.1 kbar hydrostatic pressure. The resistivity decreases slightly over the entire temperature range, but no superconducting transition or changes in the non-Fermi-liquid behavior are observed under pressure. It is estimated that significantly higher pressures are likely required before sizable changes in the properties of SrIrO3 will occur.  相似文献   

19.
The temperature dependence of magnetization and magnetic susceptibility and hydrostatic pressure effect on the Surie temperature (dTc/dP) are measured for (Co1-xMnx)2B (0?x?0.4) amorphous alloys and the results are compared with those of crystalline compounds with the same composition. The Curie temperature decreases linearly with an increasing Mn content but magnetization shows a maximum around x=0.15. The reciprocal magnetic susceptibility of all the prepared alloys obeys the Curie-Weiss law above Tc. The magnitude of the negative value of dTc/dP decreases linearly with increasing x from about 1.1 K/kbar (x=0) to zero (x=0.4), the composition dependence of which is opposite to that of the crystalline compound. The composition dependence of the average magnetic moment per transition metal atom and the Curie temperature and dTc/dP are analysed on the basis of the local environment and the pair order interaction mode, respectively.  相似文献   

20.
The pressure dependence of the two CDW transition temperatures (Td1? 350 K and Td2 ~ 190 K) in 1T-TaS2 has been investigated by measuring the resistivity up to 5 kbar. It is found that the thermal hysteresis of the phase transition at Td2 is very sensitive to the pressure and is interpreted by the phenomenological Landau theory including cubic term.  相似文献   

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