共查询到20条相似文献,搜索用时 15 毫秒
1.
M. Ragwitz F. Wegner 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,8(1):9-17
We report Nuclear Magnetic Resonance studies of CeAuAl3 and LaAuAl3 at frequencies between 1.30 and 76.91 MHz and at temperatures from up to . CeAuAl3 is a new heavy-electron compound which orders antiferromagnetically at . For the two inequivalent Al sites of CeAuAl3, the transferred hyperfine couplings and are relatively small compared to those in other Ce compounds. The nuclear quadrupolar coupling constants e2qQ
/
h are 2.9 MHz and 7.8 MHz, respectively. We suggest that the magnetic structure of the ordered state below is of a simple spiral type with the ordered Ce moments arranged ferromagnetically within the (
ab
) planes of the tetragonal crystal lattice. Based on this magnetic structure we estimate a 25% reduction of the Ce moments,
most likely due to Kondo screening. At high temperatures, in the paramagnetic state of CeAuAl3, the spin-lattice relaxation rate T1
-1
is dominated by the fluctuations of the localised Ce moments. At , T1
-1
is , more than two orders of magnitude larger than for the reference compound LaAuAl3. For temperatures lower than
T1
-1
decreases as a function of (
T
/
H
) and below , displays a linear-in-T behaviour, strongly enhanced compared to the reference compound LaAuAl3.
Received: 5 May 1998 / Received in final form: 16 July 1998 / Accepted: 20 July 1998 相似文献
2.
P. Vonlanthen J.L. Gavilano B. Ambrosini H.R. Ott Y. Aoki H. Sugawara H. Sato 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,9(1):15-20
We report the results of 69Ga- and 71Ga-NMR measurements on NdGa2 at temperatures between 0.1 and and in applied magnetic fields between zero and 74 kOe. NdGa2 orders antiferromagnetically below and undergoes several metamagnetic transitions in external magnetic fields. In zero applied magnetic field and below the temperature dependence of the spin-lattice relaxation rate T1
-1
(
T
) shows a large linear-in-T term, about two orders of magnitude higher than for the reference compound LaGa2. This strong enhancement confirms the presence of low-energy excitations in the antiferromagnetic phase of NdGa2 as was previously indicated by specific heat data. Above , T1
-1
(
T
) is dominated by an exponential term, which we associate with excitations between the lowest energy levels of the f-electron system. The separation of these energy levels is determined by exchange, crystal-field and Zeeman interactions.
Received 3 September 1998 and Received in final form 3 November 1998 相似文献
3.
Y.M. Yarmoshenko M.I. Katsnelson E.I. Shreder E.Z. Kurmaev A. Slebarski S. Plogmann T. Schlathölter J. Braun M. Neumann 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,2(1):1-3
The XPS MnL-spectra of Co2MnSn, a nearly half-metallic ferromagnet (HMF) and Pd2MnSn were investigated. The most drastical feature of the spectra observed is the well-defined magnetic splitting of the Mn
2p
3/2
, 2p
1/2
lines. This gives direct evidence of the existence of well-defined local magnetic moments in Heusler alloys in comparison
with other itinerant-electron ferromagnets. The calculations of Mn2p XPS spectra of these materials were carried out using
a fully relativistic generalization of the one-step model of photoemission and show excellent agreement with experiment.
Received: 31 October 1997 / Received in final form: 28 November 1997 / Accepted: 18 December 1997 相似文献
4.
5.
N.V. Baranov E. Bauer R. Hauser A. Galatanu Y. Aoki H. Sato 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,16(1):67-72
Electrical resistivity and calorimetric measurements on Dy
3
Coshow that below the Néel temperature (T
N
=44 K) the non-collinear antiferromagnetic structure exhibits field-induced magnetic phase transitions of a first-order type
along all principal axes, accompanied by a strongly anisotropic giant magnetoresistance and by a change of the Sommerfeld
coefficient of the specific heat. Quantum tunnelling of the magnetization appears to be possible for T
< 0.6 K.
Received 15 July 1999 and Received in final form 6 December 1999 相似文献
6.
I.S. Oliveira 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,14(1):43-46
Some metallic quantities are calculated on the grounds of Tsallis generalized statistics: the specific heat at constant volume,
c
V
(T); the chemical potential, ; the Pauli paramagnetic susceptibility, and the Korringa constant, . First it is found that for a general value of q, the Sommerfeld expansion series will exhibit both, odd and even terms, contrary to what is obtained if we use the Fermi-Dirac
(FD) statistics, where only even terms appear. It follows that: (i) the specific heat coefficient, , is q-dependent, but the temperature dependence of cV remains linear, as in the FD case; (ii) the Fermi energy, , differs from the chemical potential by a linear term in T, and not quadratic, as in FD, the same happening for ; (iii) the Korringa constant is q-dependent, but not
T-dependent. In the limit the results of FD statistics are recovered. Metallic thin films and multilayers exhibiting fractal surface structures are
possible systems where the present results could be tested.
Received 30 June 1999 and Received in final form 7 September 1999 相似文献
7.
M. Gómez Berisso P. Pedrazzini J.G. Sereni O. Trovarelli C. Geibel F. Steglich 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,30(3):343-349
We present electrical resistivity and specific heat measurements of alloys on the Rh rich side of the phase diagram of the
Ce(Rh1-xPdx)2Si2 system. We compare these results with those obtained at intermediate and low Rh concentrations. The analysis of the concentration
and temperature dependence of the entropy and of the scaling behaviour of C
el
(
T
) and ρ(
T
) clearly confirm a separation of the magnetic phase diagram into two regions: the region x
≤0.3, showing a concentration independent characteristic temperature for the 4
f-electrons with T
0
≈ 45
K, while for x
> 0.3, T0 decreases to T
0
(
x
= 1) ≈ 15
K. At low Pd-content, TN decreases very rapidly from T
N
= 36
K in pure CeRh2Si2 to T
N
= 18
K at x
= 0.1. With higher Pd concentration TN stabilizes at T
N
≈ 15
K whereas the magnitude of the anomalies in C
el
(
T
) and in the susceptibility around TN are further reduced and disappear at x
≈ 0.3. This differs from the behavior found on the Pd-rich side, where TN decreases continuously to zero with increasing Rh content. The pronounced differences observed between both phase boundaries
and the drastic effect of doping on the Rh rich side suggest an itinerant character in CeRh2 Si2, in contrast with the localized character of CePd2Si2. Further evidence for the itinerant character of CeRh2Si2 is given by the ρ(
T
) dependence observed for x
≤0.3, which scales with ρ(
T
) of the prototype itinerant compound YCo2.
Received 31 December 2001 / Received in final form 6 July 2002 Published online 19 December 2002
RID="a"
ID="a"e-mail: berisso@cab.cnea.gov.ar 相似文献
8.
Summary The direct-current resistivity, β, and Hall coefficient,R
H, of lightly dopedn-type InP samples were measured at temperatures (T) down to 12K and magnetic fields up to 4.8 kG. A sharp exponential increase in β, asT was decreased, was observed for temperatures below 80 K. The Hall coefficient showed a similar trend,i.e. R
H increased sharply asT was reduced below 80 K. This is attributed to the freeze-out of conduction electrons onto their donor sites. The donor activation
energy,E
d, calculated from the temperature dependence of the resistivity, was less than the theoretical prediction. An enhanced dielectric
constant would be a possible candidate for such behaviour. The initial decrease in β (asT is reduced) recorded in the higher-temperature region is due to impurity scattering probably combined with lattice scattering.
The authors of this paper have agreed to not receive the proofs for correction. 相似文献
9.
E. Bauer N. Pillmayr E. Gratz G. Hilscher D. Gignoux D. Schmitt 《Zeitschrift für Physik B Condensed Matter》1987,67(2):205-210
The temperature dependence of the electrical resistivity, thermopower, specific heat, susceptibility and magnetization of CeCuAl3 are presented. CeCuAl3 behaves as a Kondo lattice system with antiferromagnetic ground state properties (T
N
2.8 K). The valency of Ce in this tetragonal compound is close to 3 and the overall crystal field splitting found from our results is about 150 K. The Kondo temperatureT
K
in the crystal field ground state, estimated from the magnetic susceptibility and the specific heat, is of the order of 8 K. 相似文献
10.
V.Yu. Irkhin M.I. Katsnelson 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,30(4):481-486
Peculiarities of transport properties of three- and two-dimensional half-metallic ferromagnets are investigated, which are
connected with the absence of spin-flip scattering processes. The temperature and magnetic field dependences of resistivity
in various regimes are calculated. The resistivity is proportional to T
9/2 for T < T
* and to T
7/2 for T > T
*, T* being the crossover temperature for longitudinal scattering processes. The latter scale plays also an important role in magnetoresistance.
The contribution of non-quasiparticle (incoherent) states to the transport properties is discussed. It is shown that they
can dominate in the temperature dependence of the impurity-induced resistivity and in the tunnel junction conductivity.
Received 16 September 2002 / Received in final form 6 November 2002 Published online 31 December 2002 相似文献
11.
B. Andraka R. Pietri S.G. Thomas G.R. Stewart E.-W. Scheidt T. Schreiner 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,12(1):55-59
A comprehensive study of the relationship between the electronic specific heat coefficient () and the temperature square coefficient (A) of the electrical resistivity for a single, cubic, heavy fermion alloy system, UPt5-xAux is presented. In this alloy system, whose low temperature properties are consistent with the Fermi-liquid behavior, varies by more than a factor of 10 while the corresponding A coefficient changes by a factor larger than 200. A tracks changes in fairly well, but , postulated to have a universal value for heavy fermions, is not constant and varies from about 10-6 (x = 0, 0.5) to 10-5
cm (mol K/mJ)2 (x
> 1.1), thus from a value typical of transition metals to that characteristic of other heavy fermion compounds. We have found a
correlation between and magnetic characteristics such as the paramagnetic Curie-Weiss temperature and the low temperature magnetic susceptibility
divided by .
Received 29 January 1999 相似文献
12.
W. Felsch S. G. Kushnir K. Samwer H. Schröder R. van den Berg H. v. Löhneysen 《Zeitschrift für Physik B Condensed Matter》1982,48(2):99-107
The amorphous alloy Ce75.5Co24.5 prepared by melt spinning has been studied through measurements of the magnetic susceptibility, magnetization, electrical resistivity, thermoelectric power and specific heat. The results are interpreted in terms of a homogeneous intermediate valence state of the Ce ions. This is inferred from a temperature-independent magnetic susceptibility at low temperature and the absence of magnetic ordering, a large linear term in the specific heat, and aT
2 dependence of the electrical resistivity at low temperature followed by a steep increase with temperature up to 50 K. At this temperature, the thermoelectric power displays a maximum. The intrinsic properties are partially obscured at low temperatures by a contribution from roughly a few percent of magnetic impurities, presumably Ce3+ ions. They manifest themselves by an increase of the susceptibility towards low temperatures and by a broad Schottky-like contribution to the specific heat resulting from the excitation of magnetic clusters.Dedicated to Prof. Dr. S. Methfessel on the occasion of his 60th birthday 相似文献
13.
N.A. Babushkina L.M. Belova E.A. Chistotina O.Yu. Gorbenko A.R. Kaul B. Güttler K.I. Kugel 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,19(3):409-415
The effect of
16
O
→
18
O isotope substitution on electrical resistivity, magnetoresistance, and ac magnetic susceptibility was studied for La0.35Pr0.35Ca0.3MnO3 epitaxial thin films deposited onto LaAlO3 and SrTiO3 substrates. For the films on LaAlO3, the isotope substitution resulted in the reversible transition from a metal-like to insulating state. The applied magnetic
field ( H
≥ 2
T) transformed the sample with 18O back to the metallic state. The films on SrTiO3 remained metallic at low temperatures for both 16O and 18O, but the shift of the resistivity peak corresponding to onset of metallic state exceeded 63 K after
16
O
→
18
O substitution. The temperature dependence of both resistivity and magnetic susceptibility was characterized by hysteresis,
especially pronounced in the case of the films on LaAlO3. Such a behavior gives certain indications of the phase separation characteristic of interplay between ferromagnetism and
charge ordering.
Received 11 February 2000 and Received in final form 13 September 2000 相似文献
14.
E.F. Wassermann B. Rellinghaus T. Roessel J. Kästner W. Pepperhoff 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,5(3):361-365
We measured the thermal expansion and the specific heat of TixFe100-x alloys with x
= 30.5, 32.5 and 35, all with hexagonal C14 laves phase structure (MgZn2) like TiFe2, and determine the temperature dependence of the magnetic contributions to the thermal expansion and the specific heat cmag. For fixed composition and c
mag
(
T
) show the same type of behavior, demonstrating that both anomalies are of the same microscopic nature. They originate from
moment-volume fluctuations (antiferromagnetic Invar-effect) as a comparison with total energy calculations as a function of
atomic volume and moment for TiFe2 reveals.
Received: 26 January 1998 / Accepted: 17 April 1998 相似文献
15.
Experimental results on dc and ac susceptibility, magnetization and magnetic relaxation, specific heat, electrical resistivity and magnetoresistivity up to 8?T are reported for the novel ternary uranium aluminide U3Co4.55Al11.45. The temperature dependence of the dc susceptibility shows a cusp at a characteristic temperature T f?=?8–10?K that depends weakly on the applied magnetic field. The observed pronounced difference between the ZFC and FC magnetizations, as well as the decay in the remanent, both give evidence that a highly irreversible, frozen state is formed below T f which is reminiscent of spin-glass behaviour. The real and imaginary parts of the ac susceptibility show that the corresponding T f peaks are only slightly dependent on frequency. Electrical resistivity measured at zero and in fields up to 8?T indicates that the Kondo-like state becomes dominant at temperatures above T f. 相似文献
16.
M. Putti E. Galleani d'Agliano D. Marrè F. Napoli M. Tassisto P. Manfrinetti A. Palenzona C. Rizzuto S. Massidda 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,25(4):439-443
We report measurements of the resistivity, ρ, and the Seebeck coefficient, S
, of a MgB2 sintered sample, and compare S with theoretical calculations based on precise electronic structure calculations. ρ is fitted well by a generalized Bloch-Grüneisen equation with a Debye temperature Θ
R
of 1050 K. S is given by the sum of a diffusive and a phonon drag term and the behavior in the temperature region T
c
<
T
< 0.1Θ
R
follows the relationship AT+BT3. The phonon drag term indicates a strong electron-phonon interaction. The diffusive term, compared with calculations, suggests
that σ bands give the main contribution to the Seebeck effect.
Received 16 November 2001 and Received in final form 21 December 2001 相似文献
17.
Tomoyuki Sekine Kunimitsu Uchinokura Haruo Iimura Ryozo Yoshizaki Etsuyuki Matsuura 《Solid State Communications》1984,51(4):187-189
The successive phase transitions of the cubic spinel structure CuV2S4 have been studied by the electrical resistivity and the specific heat. In the resistivity and the specific heat two anomalies have been observed at T1~91 K and T3≈55 K. The specific heat indicates that the phase transition at T1 is in the vicinity of a tricritical point, where the resistivity has a small sharp peak. On the other hand, the specific heat shows a step at T3, where a hysteresis of the resistivity indicates the existence of the first-order phase transition. 相似文献
18.
《Journal of magnetism and magnetic materials》1994,135(2):L129-L134
We report the effect of Ce substitution for U in the heavy-electron antiferromagnetic superconductor UPd2Al3. CePd2Al3 is an established non-superconducting heavy-electron system which undergoes antiferromagnetic ordering below 2.8 K. Thus studies on U1−xCexPd2Al3 system provide a unique opportunity to observe the evolution from a 4f heavy-electron state to a 5f heavy-electron state. We have measured the resistivity and magnetic susceptibility from 1.5 to 300 K and the heat capacity from 2 to 20 K for several U1−xCexPd2Al3 samples. Our studies show that the antiferromagnetic (AF) ordering temperature (TN) of U1−xCexPd2Al3 does not decrease monotonically from TN = 14 K for UPd2Al3 to TN = 2.8 K for CePd2Al3 but rather shows a local maximum of 5 K near x = 0.4. 相似文献
19.
20.
C. Vadla 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1998,1(3):259-264
The total rate coefficient k for the energy pooling process has been measured in dependence on the ratio of the number densities of the Cs 6P fine-structure sublevels. The measurements
were performed applying the laser fluorescence method. From the set of the obtained data for k, the rate coefficients for the particular collisions were derived. The obtained values for the and collisions at T
= 600 K are , and , respectively. The value for k1 and the estimate for k3 are consistent with the data previously published by other authors. The rate coefficient k2 is reported for the first time.
Received: 10 June 1997 / Revised: 13 October 1997 / Accepted: 5 January 1998 相似文献