共查询到20条相似文献,搜索用时 46 毫秒
1.
G.M. Luke K. Kojima M. Larkin J. Merrin B. Nachumi Y.J. Uemura G.M. Kalvius A. Brückl K. Neumaier K. Andres G. Nakamoto M. Sirasi H. Tanaka T. Takabatake H. Fujii M. Ishikawa 《Hyperfine Interactions》1997,104(1-4):199-203
We present zero and longitudinal field μ SR measurements of single crystal and polycrystalline specimens of the heavy fermion
compound CePt2Sn2. Above 1 K the behaviour of the two samples is indistinguishable; the muon 1/T_1 increases with decreasing temperature until
25 K when it plateaus. The 1/T_1 relaxation rate differs strongly for the two cases below \sim\,0.8\ K. At 0.1 K a rate of
about 20 μ s-1 is seen in the polycrystal while in the single crystal it is only about 5 μ s-1. Even more revealing is the fact that longitudinal field decoupling spectra at very low temperatures demonstrate an essentially
static spin system to be present in the polycrystalline material while the single crystal shows definite dynamic spin properties.
We conclude that, in the presence of the distortion, long range magnetic order occurs below 0.9 K while in tetragonal symmetry
long range order is suppressed (probably due to frustration) and spin fluctuations remain for T\rightarrow0.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
2.
J. R. Kempton R. F. Marzke D. G. Fleming A. C. Gonzalez S. K. Leung J. J. Pan P. W. Percival M. Senba A. Tempelmann 《Hyperfine Interactions》1991,65(1-4):811-817
Results of the first μSR studies using Merck FO Optipur silica powder, which contains paramagnetic impurities at the ppb level
and has a surface area of 610±20 m2/g. are reported. Above 20 K, the transverse field muonium relaxation rate is roughly constant at 0.5 μs−1. Upon the addition of oxygen at ppm levels, the relaxation rate increases linearly with O2 concentration in the temperature range from 40–100 K yielding two-dimensional depolarization rate constants on the order
of 10−4 cm2 molecule−1 s−1. As the temperature is increased further, both oxygen and muonium desorb from the surface yielding a three-dimensional rate
constants at 300 K of 3.1(3)×10–10−10 cm3 molecule−1 s−1, in agreement with the gas phase value. Longitudinal field measurements suggest that MuO2 is formed and is able to spin exchange with other oxygen molecules. 相似文献
3.
D. W. Cooke R. H. Heffner R. L. Hutson M. E. Schillaci J. L. Smith J. O. Willis D. E. Maclaughlin C. Boekema R. L. Lichti A. B. Denison J. Oostens 《Hyperfine Interactions》1986,31(1-4):425-430
Positive muon spin relaxation experiments have been conducted on the heavy-fermion superconductor UPt3 in both the normal and superconducting states for zero, transverse, and longitudinally applied magnetic fields. Below 6 K
in zero applied field, the μ+ relaxation rate is approximately twice that expected from195Pt nuclear dipolar relaxation alone. Transverse- and longitudinal-field measurements show that the observe relaxation rate
depends on magnetic field and is quasistatic in origin. It is suggested that the onset of very weak (≈10−3 μB/U atom) magnetic ordering below approximately 6 K is responsible for the observed increase in the relaxation rate. μ+ Knight shift measurements in the normal state of UPt3 show a temperature dependent shift Kμ which tracks the bulk susceptibility X. From the Kμ vs. X plot, a μ+ hyperfine field of approximately 100 Oe/μB is extracted. 相似文献
4.
H.‐H. Klauß M. Hillberg W. Wagener M. Birke F.J. Litterst E. Schreier A. Kratzer G.M. Kalvius Y. Haga T. Suzuki 《Hyperfine Interactions》1997,104(1-4):177-180
We report on zero field and longitudinal field μSR experiments on a CeAs single crystal between 3.3 and 12 K. Below the antiferromagnetic
transition at 7.5 K a spontaneously precessing signal with a saturation frequency of \approx25 MHz representing the full sample
amplitude has been found. From an analysis of the field dependence of the relaxation rate of this signal in \langle 100\rangle
and \langle 110\rangle crystal orientation parallel to the muon spin and the applied longitudinal field, a \langle 100\rangle
orientation of the local field at the muon site is concluded. This supports an AF‐I single‐\veck magnetic ordering.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
5.
M. Koch K. Maier J. Major A. Seeger W. Sigle W. Staiger W. Templ E. Widmann R. Abela V. Claus M. Hampele D. Herlach 《Hyperfine Interactions》1991,65(1-4):1039-1045
μ− SR experiments have been performed on Si between room temperature and 6 K. The amplitude of the muon spin precession signal
in an applied magnetic field of 0.04 T decreased below 30 K. A zero-field measurement at 6 K revealed a μ− spin precession frequency of 650 MHz. The muonic atom represents an aluminium acceptor in the silicon matrix, its electronic
state is responsible for the μSR signal. A possible influence of the γ recoil produced by the X-ray cascade is discussed. 相似文献
6.
M. Hillberg M.A.C. de Melo H.H. Klauß W. Wagener F.J. Litterst P. Adelmann G. Czjzek 《Hyperfine Interactions》1997,104(1-4):221-226
The magnetic correlations in Nd2-yCeyCuO4 have been studied by zero and longitudinal field μSR. Nd1.8Ce0.2CuO4 reveals a saturation of the muon relaxation rate below 0.5 K. Even down to 70 mK LF spectra evidence spin fluctuations in
the dynamic regime with a rate of \sim 109 s-1 excluding long range magnetic order or spin glass freezing. The average Nd moment is estimated to be \approx 0.2\muB, i.e., strongly reduced from the value determined for the ground state Kramers doublet of Nd2CuO4. Extending former μSR measurements on Nd2CuO4, a gradual enhancement of the internal field has been detected below 10 K which is accompanied by an increase of the relaxation
rate. These results are attributed to the development of ordered Nd moments.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
7.
S. R. Kreitzman T. Pfiz S. Sun-Mack T. M. Riseman J. H. Brewer D. Ll. Williams T. L. Estle 《Hyperfine Interactions》1991,64(1-4):561-566
The ionization of muonium centers in Si and GaAs have been studied using radio frequency (RF) resonant techniques. In Si all
three muonic centers are detectable by RF. No evidence was found for delayed Mu and Mu* states at any temperature. However, our results on the diamagnetic final state (μ
f
+
) show that it is composed of prompt fractions (as seen by conventional μSR) and delayed fractions arising from the ionization
of Mu* and Mu. We observe a full μ
f
+
fraction at 317 K when the Mu relaxation rate is above 10 μs−1. GaAs differs from the situation in Si in that we observed only a partial conversion of Mu* and Mu to a μ+ final state up to 310 K in spite of the fact that the transverse field relaxation rates become very high at 150 and 250 K
respectively. 相似文献
8.
Krishnamurthy V.V. Watanabe I. Nagamine K. Geibel C. Sparn G. Steglich F. 《Hyperfine Interactions》1999,120(1-8):607-610
We report muon spin relaxation (μ+SR) studies on the magnetic phase diagram of Ce(Cu1-xNix)2Ge2 polycrystals for 0.5≤ x ≤ 0.8. A sharp magnetic transition, evidenced by the appearance of a fast Gaussian relaxation component
σ, has been observed in the x = 0.5 alloy at 4.0 K in zero applied field. The average local field < Bμ> at the stopping sites of the muons, extracted from σ, exhibits a linear temperature dependence. We associate these features
with an incommensurate spin density wave (SDW) ordering. Magnetic ordering, either long range or short range, and signatures
of non-Fermi liquid behaviour have not been observed down to 2.0 K at x = 0.8.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
9.
L. Asch S. Barth F. N. Gygax G. M. Kalvius A. Kratzer F. J. Litterst K. Mattenberger W. Potzel A. Schenck O. Vogt 《Hyperfine Interactions》1986,31(1-4):443-446
UAs has the NaCl structure and undergoes a first order transition into a type I (single k) antiferromagnetic state at 123
K, followed by a second first order transition at 62 K into a type IA (double k) antiferromagnetic structure. μSR spectra
of a powder sample were taken in zero and transverse fields up to 0.3 T. They cover the paramagnetic and the two antiferromagnetic
states. The most significant features of our data are: i) a first increase of relaxation rate below T=180 K; ii) a sudden
jump in both, relaxation rate and frequency shift at T=123 K, together with a small decrease in initial asymmetry (≈15%);
iii) no μ+ spin rotation in zero field in the type I state; iv) an overlay, of 3 spectra in the type IA state. Two of these spectra
show spin rotation in zero field. Their frequencies are clearly temperature dependent. In a transverse field of 5 and 10 mT
the external field adds nearly fully to the internal field.
Work supported in part by the Bundesministerium fur Forschung und Technologie, Federal Republic Germany. 相似文献
10.
F.N. Gygax A. Amato M. Pinkpank A. Schenck I.S. Anderson G. Solt T.J. Udovic 《Hyperfine Interactions》1997,106(1-4):91-95
In Sc and \alpha\mbox-ScH_x below 40 K two μ+ states are formed: a tunnelling state extending over two adjacent tetrahedral (T) interstices sharing one face in the ab‐plane
of the hcp host lattice and a static μ+–Sc–H configuration analog to the T‐pair state formed by two H atoms across a Sc site along the crystalline c‐axis. This explains
perfectly the high transverse‐field (TF) μSR measurements at low temperature and allows a qualitative understanding of the
temperature dependence.
The modelling of the low TF measurements requires in addition the consideration of the electric field gradient (EFG) components
acting on the Sc nuclei near the μ+, i.e., of the radial EFG due to the μ+ and of the axially symmetric crystal field. The magnetic field dependence of the anisotropic μ+SR relaxation rate is strongly influenced by the H‐concentration in the solid solution system.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
11.
P. Dalmas de Réotier J. P. Sanchez A. Yaouanc S. W. Harris O. Hartmann E. Karlsson R. Wäppling D. Gignoux B. Gorges D. Schmitt Ph. L'Héritier A. Weidinger P. C. M. Gubbens 《Hyperfine Interactions》1991,64(1-4):389-394
Zero-field μSR studies of some hexagonal intermetallic compounds are described. Our LaNI5 data provide information on the muon localisation site. This site could be one of the deuterium sites deduced from neutron
diffraction. A comparison of the temperature dependence of the exponential damping rate, λ(T), of our samples shows that λ(T) is strongly influenced by crystal field effects. The TbNi5 spectra exhibit two components forT<60 K. We discuss the possible explanations of this result. We see a μSR signal below the magnetic phase transition in GdNi5. This makes the study of the spin-lattice relaxation rate possible in the ordered magnetic state. 相似文献
12.
Machi I. Z. Connell S. H. Sellschop J. P. F. Bharuth-Ram K. 《Hyperfine Interactions》2001,136(3-8):723-726
A preliminary study of the diamagnetic (μd) and the paramagnetic (Mu
T
) states in a synthetic 13C diamond has been performed using the Transverse Field Muon Spin Rotation method. This system could be used to verify the
quantum diffusion behaviour observed before, however, with a more reliable extraction of the hopping rate. The results were
obtained in an applied magnetic field of 7.5 mT and at sample temperatures of 10 K, 100 K and 200 K. The prompt fraction,
f, of the μd state remains constant at 22(5)% in the range 10–200 K; that of the Mu
T
state increases from 53(10)% at 10 K to 78(10)% at 200 K. The fractions of the two states add to 100% at 200 K, suggesting
non-population of the bond-centred state, MuBC, which is often observed in other diamond samples. The μd state has a spin relaxation rate of 0.20(5) μs−1, in contrast to the zero value obtained in type II diamond samples. This indicates appreciable interaction of the μd state with the 13C atoms. The Mu
T
state has a large spin relaxation rate ranging from 3.0(5) μs−1 at 10 K to 7.0(5) μs−1 at 200 K, consistent with values obtained in diamond samples with defects. This work is part of ongoing studies of muon/muonium-defect
interactions in diamonds.
This revised version was published online in September 2006 with corrections to the Cover Date. 相似文献
13.
H.‐H. Klauß M. Hillberg W. Wagener M.A.C. de Melo F.J. Litterst M. Fricke J. Hesse E. Schreier 《Hyperfine Interactions》1997,104(1-4):319-323
The spin dynamics in the reentrant spin glass ( Fe0.65 Ni0.35)1-x Mn_x has been studied by zero, longitudinal and transverse field μSR. In the ferromagnetic reentrant and pure spin glass
regimes (x\leqslant 0.175), zero field experiments reveal a stretched exponential muon relaxation with a universal behaviour
of the dynamic exponent \beta above the spin glass transition. There are no qualitative differences between the ferromagnetic
and paramagnetic phases. In transversal field μSR experiments the divergence of the relaxation rate close to the spin glass
transition is suppressed for manganese doping up to x=0.113 but enhanced for slightly higher doping (x\geqslant 0.12). We
understand this behaviour as a crossover from an itinerant to a more localized state of the 3d electron system. This is also
supported by the fact that in the highly doped regime with dominant antiferromagnetic interactions the muon relaxation rate
diverges above the antiferromagnetic transition temperature.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
14.
The microscopic state of the positive muon in the transition metal dichalcogenide 2H-NbSe2 was studied using the muon spin relaxation method (μ+SR). We found that the μ+SR spectra consist of two components. The ratio of the two components and the dynamics of the muon change at 140 K, at the
charge-density-wave transition temperature (32 K), and again at the superconducting transition temperature (7 K). We discuss
the relation between conduction electron properties and the muon's behavior.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
15.
S. Barth H. R. Ott F. Hulliger F. N. Gygax A. Schenck T. M. Rice 《Hyperfine Interactions》1986,31(1-4):403-405
Muon-spin-rotation and relaxation measurements performed on polycrystalline UCd11 give first direct evidence for an antiferromagnetic phase transition at 5 K. As far as probed by the positive muon the behaviour
close to the phase transition is clearly contrasted to that in other magnetic heavy-electron materials investigated by μ+SR, e.g. U2Zn17 and UCu5, because in UCd11 longitudinal field measurements reveal dynamic relaxation effects which are attributed to the critical slowing down of the
uranium 5f-moments. No signal could be observed in the ordered regime because of a large dipolar field spread. 相似文献
16.
W.A. MacFarlane R.F. Kiefl J.E. Fischer S.R. Dunsiger J.E. Sonier J. Chakhalian K.H. Chow 《Hyperfine Interactions》1997,105(1-4):77-82
We report ZF μSR measurements in Cs1C60 at low temperature and LF μSR in the superconductor Rb3C60. In Cs1C60, the internal magnetic field distribution is broad and static, and the relaxation at 1.9 K resembles that of a spin density
wave. In Rb3C60, we observe a strong field dependence to the coherence peak in the LF relaxation rate of endohedral muonium ( Mu@C60) at anomalously low field and a residual low temperature relaxation.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
17.
T.N. Mamedov I.L. Chaplygin V.N. Duginov V.G. Grebinnik K.I. Gritsaj V.G. Olshevsky V.Yu. Pomjakushin A.V. Stoykov V.A. Zhukov I.A. Krivosheev B.A. Nikolsky A.N. Ponomarev V.N. Gorelkin 《Hyperfine Interactions》1997,105(1-4):345-349
The dependence of the residual polarization of negative muons in n‐type Si with impurity concentration (1.6\pm 0.2)\times
1013\ cm-3 on temperature in the 10–300 K range has been investigated. Measurements were carried out in external magnetic field of 0.08
T transverse to the muon spin. Muon spin relaxation and frequency shift were observed at temperatures below 30 K. The relaxation
rate at 30 K is equal to 0.25\pm 0.08\,μ s-1. The frequency shift at 20 K is equal to 7\times 10-3. Both the relaxation rate and the frequency shift grow with decrease of temperature. Below 30 K the relaxation rate is well
described by the dependence \varLambda=bT-q, where q=2.8.
An analysis of present and earlier published data on behavior of negative muon polarization in silicon is given. A possible
mechanism of relaxation and frequency shift of muon spin precession in silicon is considered.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
18.
V. N. Gorelkin V. G. Grebinnik K. I. Gritsai V. N. Duginov V. A. Zhukov T. N. Mamedov V. G. Ol’shevski V. Yu. Pomyakushin A. V. Stoikov I. L. Chaplygin I. A. Krivosheev B. A. Nikol’skii A. N. Ponomarev 《JETP Letters》1996,63(7):566-571
The residual polarization of negative muons in n-type silicon with impurity density (1.6±0.2) · 1013 cm−3 is investigated as a function of temperature in the range 10–300 K. The measurements are performed in an external magnetic
field of 0.08 T oriented transversely to the spin of the muons. Relaxation of the muon spin and a shift of the precession
frequency are observed at temperatures below 30 K. The relaxation rate at 30 K equals 0.25±0.08 μs−1. The shift of the precession frequency at 20 K equals 7 · 10−3. Both the relaxation rate and the shift of the precession frequency increase as the temperature decreases. At temperatures
below 30 K the relaxation rate is described well by the relation Λ=bT
−q
, where q=2.8±0.2.
Pis’ma Zh. éksp. Teor. Fiz. 63, No. 7, 539–543 (10 April 1996) 相似文献
19.
R. Scheuermann J. Schmidl A. Seeger Th. Stammler D. Herlach J. Major 《Hyperfine Interactions》1997,106(1-4):295-300
Longitudinal‐field μSR methods, e.g., radio‐frequency μ+ spin resonance (RFμSR), are well suited to investigate dynamic processes that destroy the phase coherence of the muon spin
ensemble. Additional information on relaxation processes of the muon species under investigation is obtained from time‐differential
(TD) data acquisition.
In this paper we describe the set‐up of a TD‐RFμSR spectrometer installed at the ISIS pulsed muon facility at the Rutherford
Appleton Laboratory (RAL, Chilton, UK). As an example, results of TD‐RFμSR measurements on muons in diamagnetic environment
μd in a boron‐doped silicon sample under illumination at 55 K are presented.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
20.
L. Cristofolini K. Prassides K. Vavekis A. Amato F.N. Gygax A. Schenck S. Gider D.D. Awschalom 《Hyperfine Interactions》1997,104(1-4):269-274
We present a study of the magnetic properties of the superparamagnetic ferritin system by employing zero‐field (ZF) and longitudinal‐field
(LF) μ+SR measurements. Two μ+ fractions with different depolarisation behaviour are detected, one arising from muons stopped in the organic shell and one
from muons stopped in the mineral core. The freezing of the superparamagnetic moments is evident in the temperature evolution
of the ZF relaxation rates of both fractions. It occurs gradually below \approx 60\ K and is essentially complete at \approx
11\ K. The results are consistent with a distribution of blocking temperatures which in turn reflects the distribution of
core sizes.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献