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1.
S. I. Vorob’ev A. L. Getalov E. I. Golovenchits E. N. Komarov V. P. Koptev S. A. Kotov I. I. Pavlova V. A. Sanina G. V. Shcherbakov 《Physics of the Solid State》2013,55(3):466-475
The GdMn2O5 multiferroic (a ceramic sample and a sample consisting of a large array of randomly oriented single crystals with linear dimensions 2–3 mm) has been studied by the μSR method within the temperature range 10–300 K. Three anomalies in the temperature behavior of the parameters of the muon polarization relaxation function, namely, close to the phase transition driven by the onset of long-range magnetic order in the manganese ion subsystem (T N1 = 40–41 K), near the lock-in transition initiated by an abrupt change of the wave vector of magnetic order (T L = 35 K), and close to the Gd3+ ion ordering temperature (T N2 = 15 K), have been found. An analysis of the time spectra of muon spin precession in the internal magnetic field of the samples has revealed two positions of preferable muon localization sites in samples, which differ in precession frequencies and the character of their behavior with temperature. The lower-frequency precession driven by Mn4+ ions, ferromagnetic Mn4+-Mn4+ + muonium complexes, and Gd3+ions is observed throughout the temperature region T < T N1 and is practically independent of temperature. At temperatures T < T L = 35 K, a higher-frequency precession associated with Mn3+ ions appears also. It is characterized by a temperature dependence ~(T/T N1)β with the index β = 0.39, which is typical of Heisenberg-type 3D magnets. For T < T N1, a deficiency of the rest total asymmetry is observed. This phenomenon can probably be assigned to formation of muonium, which suggests that charge transfer processes play an important role in formation of long-range magnetic order. 相似文献
2.
Fukaya A. Satooka J. Ito A. Torikai E. Nishiyama K. Nagamine K. 《Hyperfine Interactions》1999,120(1-8):615-618
The diluted antiferromagnet MnxMg1-xTiO3 transforms from the antiferromagnet (AF) to the spin-glass (SG) system at x ∼ 0.6. In order to study the microscopic nature
of spin dynamics and ordering, we performed muon spin relaxation measurements for the powder samples of x=1.0∼ 0.55 and examined
the concentration dependence. From these results, a drastic change in the spin dynamics was found to occur at x ∼ 0.6.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
3.
K. H. Münch A. Kratzer G. M. Kalvius L. Asch F. J. Litterst K. Richter 《Hyperfine Interactions》1993,78(1-4):435-438
In the paramagnetic range (T>T
N=53 K) fluctuations of the moments on uranium are too fast to produce a sizeable damping of the SR signal even close toT
N. This rules out the formation of a magnetic precursor state as seen in UAs. In the antiferromagnetic regime all contributions to the field at the muon site cancel due to symmetry. Comparison with analogous data on other uranium mono-pnictides show that the magnitude of the field distribution width in the type I-single k antiferromagnetic state is not an intrinsic property of these materials.Work supported by the German Federal Minister for Research andTechnology (BMFT) under contract number 03-KA2-TUM-4. 相似文献
4.
Christof Niedermayer 《Hyperfine Interactions》1994,86(1):797-808
A review is given of the current status of SR results on muonium states in the pure fullerenes C60 and C70 as well as on the alkali doped series of C60. In particular the results of studies of the hyperfine interaction of the muonated radicals are discussed in order to determine their electronic distribution and the rotational ordering and dynamics of the fullerenes. Unique information on the alkali doped C60 species is obtained from studies of the endohedral muonium species. 相似文献
5.
G. Michael Kalvius 《Hyperfine Interactions》1994,84(1):249-264
Zero, longitudinal and transverse field SR was carried out between 3 and 250 K in YMn2, Y0.9Tb0.1Mn2, Y0.98Sc0.02Mn2 and TbMn2. The data had to be analyzed in the frame of electronic-nuclear double relaxation. The dynamics of Mn magnetic moments in the paramagnetic state is typical for an itinerant antiferromagnet approaching magnetic order. This behavior is suppressed abruptly when the first-order transition occurs. In all samples, a part enters a randomly ordered (spin glass like) magnetic state within a certain temperature range aboveT
N as an outcome of frustration. The temperature range of existence and the fraction of the sample taking part in this stale is enhanced by the presence of Tb3+ paramagnetic ions and also by the lattice pressure in the Sc doped compound. It is suspected that muon dynamics makes the extraction of information on magnetic relaxation questionable above 150–180 K.Part of this work was funded by the German Federal Minister for Research and Technology (BMFT) under Contract No. 03-KA2-TUM. 相似文献
6.
A. Yaouanc P. Dalmas De Reotier P. C. M. Gubbens A. A. Moolenaar A. A. Menovsky C. E. Snel 《Hyperfine Interactions》1994,85(1):351-356
We report zero field and longitudinal fieldSR measurements on single crystals of the ferromagnet PrRu2Si2 (T
c15K). BetweenT=T
c and 250K we observe a quasi-static spin dynamics of the Pr3+ ion sub-lattice. BelowT
c, depending on the orientation of the initial muon beam polarisation relative to thec axis of the compound, we find either an oscillating signal or an exponential depolarisation function. These latter data allow us to get information related to the muon in PrRu2Si2. 相似文献
7.
A. Yaouanc 《Hyperfine Interactions》1984,17(1-4):355-357
We point out that
+SR relaxation timesT
1 andT
2 measured in metallic magnetic materials can sometimes be expressed in terms of the spin-spin correlation functions of the magnetic ions. We calculate these functions in a random phase approximation and notice they can strongly depend on the crystal field levels and excitations of the magnetic ions. The shortcomings of this approximation are discussed.Part of this work was done at the French Atomic Commission at Grenoble. 相似文献
8.
The derivation of a formula for the time during which a sound signal propagates between two given points A and B in a stationary gas flow is considered. It is shown that the gas flow changes the signal reception time by a quantity proportional to the consumption, regardless of the detailed velocity profile. The difference between the reception time of signals from point B to the point A and vice versa is proportional to air consumption with high accuracy. It is shown that the relative error of the obtained formula does not exceed the squared maximum Mach number in the gas flow. This allows measurement of the consumption of gas moving in a mine with an arbitrary stationary subsonic velocity field. 相似文献
9.
Nishiyama K. Higemoto W. Shimomura K. Koda A. Maruta G. Nishiyama S. W. Zheng X. G. 《Hyperfine Interactions》2001,136(3-8):289-294
Precise measurements of the local magnetic field at muon sites in CuO were performed. The temperature dependence of the local
field including spatial orientation was obtained in the ordered state. Not only zero field μSR measurements were performed,
but also external magnetic fields were applied to obtain an unambiguous determination of field direction. Multiple stages
of muon signals were observed at 55 and 80 K. An incommensurate phase between 212 K and 227 K was confirmed from the line
shapes of the local fields at the muon sites.
This revised version was published online in September 2006 with corrections to the Cover Date. 相似文献
10.
V. N. Duginov V. G. Grebinnik R. Horyn B. F. Kirillov J. Klamut I. A. Krivosheev T. N. Mamedov V. G. Olshevsky A. V. Pirogov V. Yu. Pomjakushin A. N. Ponomarev A. J. Zaleski V. A. Zhukov 《Hyperfine Interactions》1994,85(1):311-316
Zero field muon spin rotation and magnetic susceptibility experiments on investigation of magnetic properties of cuprateY
2Cu2O5 have been performed in the temperature range 4.2–30 K. Transverse fieldSR-experiments have been also carried out in order to obtain accurate information about transition temperature and to study the influence of the external magnetic field. Our data show that two magnetic phase transitions occur inY
2Cu2O5 with lowering temperature. Upper Neel temperatureT
N=13 K is consistent with previous experimental data. We obtained the temperature dependence of the local magnetic field on the muonB
(T) in the antiferromagnetic phase.B
(T) reveals a peculiarity (some change of the slope) near the temperatureT
N=7.5 K, which can be interpreted as an additional magnetic phase transition caused by a change in magnetic ordering of the copper subsystem. Applying a small external magnetic field 50 Oe leads to smearing of the peculiarity inB
(T) dependence. 相似文献
11.
A 3 W average power CO2 laser oscillating in the range of 4.3m (10°1 to 10°O transition) is described. At the same time, the laser can emit 100 W in the sequence band 00°2 to 10°1 (10.6m). It is based on a commercial system with continuous-wave discharge of 12 m length and a slow gas flow. It operates in the Q-switched mode at pulse repetition rates up to 15 kHz. The pulse peak power is 1 kW and the pulse duration is 200 ns. The deviation from the theoretical efficiency limit has been decreased by a factor 2.5 in our device, due to saturation of the pumping (sequence band) radiation. We predict an improvement by another factor of 5 (possible average power of 10 to 20 W), if one avoids the absorption in the discharge-free zones. 相似文献
12.
T. N. Mamedov V. N. Duginov V. G. Grebinnik K. I. Gritsaj V. G. Olshevsky V. Yu. Pomjakushin V. A. Zhukov B. F. Kirillov B. A. Nikolsky A. V. Pirogov A. N. Ponomarev V. A. Suetin V. N. Gorelkin 《Hyperfine Interactions》1994,86(1):717-722
The dependence of the residual polarization of negative muons in p-type Si on temperature in the 4.2–270 K range has been investigated. Measurements were carried out in external magnetic field of 0.08 T transverse to the muon spin. The impurity concentration in the sample was 2 · 1013 cm–3. Muon spin relaxation was observed at temperatures below 30 K. The relaxation rate atT=30 K is equal to 0.18±0.08s–1. The relaxation rate grows with the decrease of temperature and at 4.2 K exceeds 30s–1. The value of the residual polarization at zero timeP(t=0) is constant within the investigated temperature range.In the rangeT<30 K data on the relaxation rate are well described by the dependence =B·T–q, whereq=2.75. Power dependence of may evidence the essential role of the phonon mechanism in the relaxation of the electron momentum of the acceptor center.The authors express their gratitude to V.B. Brudanin and I.A. Yutlandov for providing the sample, and to Yu.B. Gurov for advices. 相似文献
13.
H. -H. Klauß M. A. C. de Melo F. J. Litterst L. Asch A. Kratzer S. Henneberger G. M. Kalvius K. Mattenberger F. Hulliger 《Hyperfine Interactions》1994,85(1):293-298
ZFSR experiments on CeSb and DySb reveal fast spin dynamics even in their magnetically ordered states below 16.2 and 9.5 K, respectively. Above these first order transitions both pnictides exhibit strong frequency shifts in TF pointing to some magnetic precursors. The signals below T
N
show spontaneous rotating contributions. For CeSb several commensurately modulated antiferromagnetic phases containing paramagnetic sheets are confirmed. For DySb our data favor a CoO type structure in contrast to the MnO structure proposed from neutron diffraction.Part of this work was funded by the German Federal Minister for Research and Technology (BMFT) under contracts No 03-LI3-BRA and 03-KA2-TUM-4. 相似文献
14.
《Physics letters. A》1997,228(6):363-368
The stability of the elliptical orbits of diamagnetic positronium is studied and it is found to depend only on the eccentricity ε and the combination of parameters λ = B2r0c3 (where B is the magnetic field strength and r0c the conserved guiding center). For small and large values of λ the orbits remain stable while at approximately λ = 1 unstable behavior appears when the eccentricity becomes larger than ε = 0.25. 相似文献
15.
R. Kadono J. Imazato K. Nishiyama K. Nagamine T. Yamazaki D. Richter J. M. Welter 《Hyperfine Interactions》1984,17(1-4):109-115
Diffusion of muons in high purity Cu was studied by the zero-fieldSR method at temperatures from 134 K down to 0.09 K. The experimental data show clear evidence that the muons still diffuse below 15 K; the measured diffusion rate has a minimum at around 15 K and seems to become independent of temperature below about 0.5 K. 相似文献
16.
《Journal of Magnetic Resonance (1969)》1976,21(1):17-23
The Forsén-Hoffman double irradiation method of relating exchange rates to T1 has been applied to the 13C NMR spectrum of cis-decalin. The rate of exchange can be determined for a two-site exchange problem by measuring the size of the signal at one site in the absence and presence of a radiofrequency magnetic field at the second site and by measuring T1 of the first site by the conventional (Td-π-τ-π/2)n pulse sequence. It is shown that the use of this method in conjunction with line-shape analysis provides a powerful method of accurately determining activation parameters. 相似文献
17.
A novel approach to extracting frequency spectra from transverseSR spectra is presented, based on the maximum entropy method. This has the advantages of ensuring positivity of the frequency spectra, and only deviating from a flat default level where there is statistically significant information present in the data. It allows simultaneous analysis of spectra from multiple detectors with different phases to yield a single frequency spectrum. 相似文献
18.
19.
Energy average formula of photon gas rederived by using the generalised Hermann-Feynman theorem
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By virtue of the generalised Hermann-Feynmam theorem we re-derive the energy average formula of photon gas. This is another useful application of the theorem. 相似文献
20.
The spectral dependence of the electron-phonon relaxation rate γe−ph(ℏω) in metals is studied in pump-supercontinuum-probe (PSCP) experiments with femtosecond time resolution. Investigation
of this spectral dependence, which exhibits a substantial slowing of the relaxation rate γe−ph(ℏω) near the Fermi level E
F
, using the parametrization γe−ph(ℏω)∝λ〈Ω2〉 (ℏω−E
F
)2 makes it possible to determine directly the electron-phonon interaction parameter λ〈Ω2〉. The parameter λ〈Ω2〉 for YBa2Cu3O7−δ is analyzed using this method.
Pis’ma Zh. éksp. Teor. Fiz. 70, No. 5, 329–332 (10 September 1999) 相似文献