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1.
Radioactive77Br ions were implanted at 60 keV and 270 keV into polycrystalline iron foils. The magnetic hyperfine interaction of the daughter
nucleus77Se in the 250 keV isomeric level was investigated using the perturbed angular correlation technique and fast BaF2 detectors. The Larmor frequency at room temperature was determined as ωL=1272(2) MHz, leading to a substitutional hyperfine field ofB
hf(SeFe)=62(6) T. The substitutional fraction rises from 21% at room temperature to about 100% at 790 K annealing temperature.
No other well-defined magnetic or electric hyperfine component attributable to impurity-defect complexes was identified. The
diffusion of Br atoms in the surface region during the annealing process was studied via Rutherford backscattering with 1.0
MeV α-particles. 相似文献
2.
M. Trhlík B. Sedlák V. P. Parfenova A. L. Erzinkyan G. M. Gurevich S. V. Topalov P. Malinský V. N. Pavlov 《Hyperfine Interactions》1989,50(1-4):749-754
The low temperature nuclear orientation of54Mn in Pt99.95Fe0.05, Pt99.9Fe0.1, Pt99Fe1 and Pt88Fe12 has been studied in the temperature range 12–50 mK and in the external magnetic field range 0–1.2 T. The strong temperature
and external magnetic field dependence of the effective fieldB
eff on54Mn has been observed even in the range where the host itself is magnetically saturated. This behaviour is interpreted by noncollinearity
of the Mn magnetic moments with respect to the macroscopic magnetisation direction. 相似文献
3.
W. Schwarz E. H. Brandt K. -P. Döring U. Essmann K. Fürderer M. Gladisch D. Herlach G. Majer H. -J. Mundinger H. Orth A. Seeger M. Schmolz 《Hyperfine Interactions》1986,31(1-4):247-253
The diffusivityD
μ of positive muons (μ+) in the mixed state of superconducting high-purity, high-perfection niobium single crystals is investigated by measurements
of the relaxation of the transverse muon spin polarization (μ+SR). The method makes use of the strong magnetic field gradients existing in the mixed state of Type-II superconductors and
monitorsD
μ through the variation of the magnetic field felt by the μ+ during their diffusion through the crystals. For μ+ near the centres of the flux lines inNb it givesD
μ(4.6 K)=(8±2)·10−11m2S−1. The positive temperature coefficient ofD
μ indicates that at liquid-helium temperatures the diffusivity of μ+ inNb is mainly due to phonon-assisted tunnelling processes. 相似文献
4.
The magnetic hyperfine field of Se in nickel was measured by means of the time-differential perturbed angular correlation
(DPAC) technique, using the 755–250 keV γ-ray cascade fed in the decay of77Br. A value ofB
hf(NiSe)=+15.11(35) T was obtained at room temperature. The half-life of the 250 keV state and the anisotropy of the 755–250 keV
cascade were found to beT
1/2=9.68(6) ns andA
22=−0.454(9), respectively. 相似文献
5.
F. N. Gygax P. Birrer B. Hitti E. Lippelt A. Schenck M. Weber 《Hyperfine Interactions》1991,64(1-4):489-495
μ
+ SR measurements have been performed in a single crystal indium sample between 12 K and 300 K with a stroboscopic μSR spectrometer.
The muonic Knight shiftK
μ and the muonic depolarization rate σ were obtained for various angles θ between the tetragonal crystallinec-axis and the direction of the external field. The isotropic part ofK
μ is only weakly temperature dependent and is consistent with the estimated Pauli spin susceptibility value. At a temperature
of 12 K the angular dependence ofM
2 (the second moment of the field distribution at the muon, obtained from the measured σ(θ) values) allows a clear determination
of the muon location — the symmetric tetrahedral site. The observed anisotropicK
μ cannot be explained by the dipoles at the In atoms responsible for the bulk magnetic susceptibility but probably originates
from an anisotropic Pauli spin susceptibility. 相似文献
6.
The magnetic properties of complex oxides Ln
2Mn2/3Mo4/3O7 (Ln=Sm, Gd, Tb, or Y) with a pyrochlore-type structure are studied in the temperature range 2–300 K. For all compounds in the
paramagnetic state, the temperature dependence of the magnetic susceptibility is described by a generalized Curie-Weiss law
with a temperature-independent component of ∼10−6 cm3/g and with a Weiss constant Θ<0 and |Θ|<16 K. At low temperatures (T<10–12 K), the compounds have spin-glass properties; they exhibit magnetic and temperature hysteresis and the typical dependences
of the imaginary and real parts of the dynamic magnetic susceptibility on temperature and the frequency of an ac magnetic
field in a wide range of magnetization relaxation times. The data obtained suggest that d electrons are responsible for the formation of frustrated exchange interactions in the compounds and that 4f electrons in the compounds with Sm or Tb provide strong magnetic-anisotropy effects.
__________
Translated from Fizika Tverdogo Tela, Vol. 46, No. 2, 2004, pp. 287–295.
Original Russian Text Copyright ? 2004 by Korolev, Bazuev. 相似文献
7.
A study is reported of the dependence of magnetoresistance Δρ/ρ on the square of magnetization σ
2 of the semiconducting spinelide Cu0.625Ga0.375Cr2Se4, which exhibits a low-temperature transition from long-range magnetic order (LRMO) to the spin glass (SG) state in strong
magnetic fields. It is shown that at the freezing temperature T
f the Δρ/ρ(σ
2) relations change their slope, and that below T
f this slope is about one half that for T>T
f. This finding, together with the earlier observation that the freezing temperature does not depend on the frequency of the
ac magnetic field in which it was measured, suggests that the spin-glass phase consists of spins of individual Cr3+ ions, and that the SG-LRMO crossover is a phase transition.
Fiz. Tverd. Tela (St. Petersburg) 40, 315–317 (February 1998) 相似文献
8.
The magnetic hyperfine field of Ta in iron was measured by means of DPAC using the 5/2+ state in181Ta. At room temperature, this field was found to be |H
hf(RT)|=6.08(7) T, which confirms the result of an earlier DPAC experiment. A hyperfine anomaly5/2Δ7/2=−4.6(23)% between the above state and the 7/2+ ground state of181Ta is deduced. 相似文献
9.
P. Kienle 《Hyperfine Interactions》1996,103(1):49-58
Experiments which led to the discovery of the heaviest, self-conjugated double magic nucleus100Sn and the bound-state β-decay of completely ionized187Re are presented.100Sn was produced by fragmentation of 1.1 A GeV124Xe beams, separated and implanted in a 4π Si-stack detector. From its decay a half-lifeT
1/2=0.94(+0.54, −0.27) s and a β+ endpoint energy ofE
β=3.4(+0.7, −0.3) MeV were determined for the 0+−1+ Gamov-Teller transition. Completely stripped187Re75+ was produced and stored in a coolerring with an energy of 351 A MeV for several hours. The products of bound-state β-decay
of187Re75+ were detected by two independent methods, which allowed to determine a half-life ofT
1/2=33±6 y for this decay, which is of importance for the calibration of the Re/Os nucleosynthesis chronometer. 相似文献
10.
D. G. Haase C. R. Gould J. E. Koster N. R. Roberson L. W. Seagondollar J. P. Soderstrum M. B. Schneider X. Zhu 《Hyperfine Interactions》1988,43(1-4):133-138
We describe searches for parity and time reversal violations in the scattering of polarized neutrons from polarized and aligned165Ho targets. We have completed a search with 7.1 and 11.0 MeV neutrons for PoddTodd terms in the elastic scattering forward amplitude of the form s. (I×K), wheres is the neutron spin,I is the target spin andk is the neutron momentum vector. The target was a single crystal of holmium, polarized horizontally along itsb axis by a 1 Tesla magnetic field. The neutrons were polarized vertically. Differences in the neutron transmission were measured
for neutrons with spins parallel (antiparallel) toI×k. The P,T violating analyzing powers were found to be consistent with zero at the few 10−3 level: ρP,T(7.1 MeV)=−0.88 (±2.02) x 10−3, ρP,T(11.0 MeV)=−0.4 (±2.88) x 10−3. We have also attempted to find enhancements with MeV neutrons in P-violation due to the term s\k. We are preparing an aligned target cryostat for investigations of PevenTodd terms {bd(I\k)(I×k)\s} in neutron scattering. The target will be a single crystal cylinder of165Ho cooled to 100 mK in a bath of liquid helium and rotated by a shaft from a room temperature stepping motor. The cylinder
will be oriented vertically and the alignment (c) axis oriented horizontally. Warming or rotation of the sample allows one to separate effects that mimic the sought-after
time reversal violating term. 相似文献
11.
Yu. N. Ovchinnikov A. M. Dyugaev 《Journal of Experimental and Theoretical Physics》1999,88(4):696-709
The magnetic field dependence of the average spin of a localized electron coupled to conduction electrons with an antiferromangetic
exchange interaction is found for the ground state. In the magnetic field range μH∼0.5T
c
(T
c
is the Kondo temperature) there is an inflection point, and in the strong magnetic field range μH≫T
c
, the correction to the average spin is proportional to (T
c
/μ H)2. In zero magnetic field, the interaction with conduction electrons also leads to the splitting of doubly degenerate spin
impurity states.
Zh. éksp. Teor. Fiz. 115, 1263–1284 (April 1999)
Published in English in the original Russian journal. Reproduced here with stylistic changes by the Translation Editor 相似文献
12.
We look at the confinement of tensor gluons (f
μν
(c)
field) in a strong gravity background and find that the strong gravity provides a trap for the confinement of colour waves
of selected frequencies. We assume that the tensorf
μν
(c)
field (mediating quanta: tensor 2+
f-meson) satisfies Einstein-like equations with a cosmological constant. The colour field satisfy equations resembling Maxwell
form of the linear theory of gravitation and see the effect off
μν
(c)
field as playing the role of a medium having space dependent dielectric permeabilities. The solution of colour field equations
resemble harmonic oscillator type wave functions with equispaced energy levels (no continuum) leading to confinement. 相似文献
13.
S. S. Murzin 《JETP Letters》1998,67(3):216-221
The conductance of doped n-GaAs films is studied experimentally as a function of magnetic field and temperature in strong magnetic fields right up to
the quantum limit (ħωc = E
F). The Hall conductance G
xy is virtually independent of temperature T until the transverse conductance G
xx is quite large compared with e
2/h. In strong fields, when G
xx becomes comparable to e
2/h, G
xy starts to depend on T. The difference between the conductances G
xx at the two temperatures 4.2 and 0.35 K depends only weakly on the magnetic field H over a wide range of magnetic fields, while the conductances G
xx themselves vary strongly. The results can be explained by quantum corrections to the conductance as a result of the electron-electron
interaction in the diffusion channel. The possibility of quantization of the Hall conductance as a result of the electron-electron
interaction is discussed.
Pis’ma Zh. éksp. Teor. Fiz. 67, No. 3, 201–206 (10 February 1998) 相似文献
14.
M. Wolf J. Ahrens R. Beck V. Hejny J.D. Kellie M. Kotulla B. Krusche V. Kuhr R. Leukel V. Metag J.C. Nacher R. Novotny V. Olmos de León R.O. Owens F. Rambo A. Schmidt M. Schumacher U. Siodlaczek H. Ströher J. Weiß F. Wissmann 《The European Physical Journal A - Hadrons and Nuclei》2000,9(1):5-8
Double neutral pion photoproduction from the proton has been measured at MAMI for photon energies between threshold and 820
MeV. The reaction was identified by an invariant mass and missing mass analysis. From threshold up to 370 MeV the total cross-section
does not exceed 30 nb. For higher energies it shows a smooth rise until it reaches a maximum of about 10 μb at E
γ = 740 MeV. Dalitz plots of m
2(π0π0) versus
m
2(p,π0) for seven bins of incident photon energy have been analysed. For E
γ > 610 MeV, a strong contribution of a sequential decay is observed with the Δ(1232)-resonance as intermediate state. A comparison
to model calculations shows that these sequential decays presumably originate from the D
13(1520) and also the P
11(1440)-resonance.
Received: 6 June 2000 / Accepted: 18 August 2000 相似文献
15.
We report the optical spectra and single crystal magnetic susceptibility of the one-dimensional antiferromagnet KFeS2. Measurements have been carried out to ascertain the spin state of Fe3+ and the nature of the magnetic interactions in this compound. The optical spectra and magnetic susceptibility could be consistently
interpreted using aS=1/2 spin ground state for the Fe3+ ion. The features in the optical spectra have been assigned to transitions within thed-electron manifold of the Fe3+ ion, and analysed in the strong field limit of the ligand field theory. The high temperature isotropic magnetic susceptibility
is typical of a low-dimensional system and exhibits a broad maximum at ∼565K. The susceptibility shows a well defined transition
to a three dimensionally ordered antiferromagnetic state atT
N=250 K. The intra and interchain exchange constants,J andJ′, have been evaluated from the experimental susceptibilities using the relationship between these quantities, andχ
max,T
max, andT
N for a spin 1/2 one-dimensional chain. The values areJ=−440.71 K, andJ′=53.94 K. Using these values ofJ andJ′, the susceptibility of a spin 1/2 Heisenberg chain was calculated. A non-interacting spin wave model was used belowT
N. The susceptibility in the paramagnetic region was calculated from the theoretical curves for an infiniteS=1/2 chain. The calculated susceptibility compares well with the experimental data of KFeS2. Further support for a one-dimensional spin 1/2 model comes from the fact that the calculated perpendicular susceptibility
at 0K (2.75×10−4 emu/mol) evaluated considering the zero point reduction in magnetization from spin wave theory is close to the projected
value (2.7×10−4 emu/mol) obtained from the experimental data. 相似文献
16.
Th. Hilberath St. Becker G. Bollen M. Gerber H. -J. Kluge U. Krönert G. Passler 《Hyperfine Interactions》1990,59(1-4):97-100
The hyperfine structure and the isotope shift of very neutron-deficient Au and Pt isotopes have been determined at the on-line
isotope separator ISOLDE/CERN by resonance ionization mass spectroscopy combined with pulsed-laser induced desorption of the
implanted radioactive sample. The changes of the mean-square charge radii were determined for the isotopes184Au (T1/2=53 s) and183Au (T1/2=42 s) as well as for 15 isotopes of platinum in the range between198Pt (stable) and183Pt (T1/2=6.5 min). The strong deformation of185Au (|β2|≃0.25) persits down to183Au. In183Pt nearly the same value of |β2| is reached but the deformation is build up rather smoothly in contrast to the neighbouring isotopes of gold and mercury.
The magnetic moment of183Pt was found to be μ1=+0.51(3)μ
N
. 相似文献
17.
Yu. G. Chukalkin A. E. Teplykh A. N. Pirogov D. G. Kellerman 《Physics of the Solid State》2010,52(12):2545-2551
The specific features of the crystal structure and the magnetic state of stoichiometric lithium manganite in the structurally
ordered Li[Mn2]O4 and disordered Li1 − δMnδ[Mn2 − δLiδ]O4 (δ = 1/6) states have been investigated using neutron diffraction, X-ray diffraction, and magnetic methods. The structurally
disordered state of the manganite was achieved under irradiation by fast neutrons (E
eff ≥ 1 MeV) with a fluence of 2 × 1020 cm−2 at a temperature of 340 K. It has been demonstrated that, in the initial sample, the charge ordering of manganese ions of
different valences arises at room temperature, which is accompanied by orthorhombic distortions of the cubic spinel structure,
and the long-range antiferromagnetic order with the wave vector k = 2π/c(0, 0, 0.44) is observed at low temperatures. It has been established that the structural disordering leads to radical changes
in the structural and magnetic states of the LiMn2O4 manganite. The charge ordering is destroyed, and the structure retains the cubic symmetry even at a temperature of 5 K. The
antiferromagnetic type of ordering transforms into ferrimagnetic ordering with local spin deviations in the octahedral sublattice
due to the appearance of intersublattice exchange interactions. 相似文献
18.
V. V. Skobelev 《Russian Physics Journal》2009,52(7):704-714
The probability and intensity of neutrino radiation of a hydrogen-like atom in the strong magnetic field B >> Z
2α2
B
0, α = e
2 = 1/137, B
0 = m
2/e = 4.41⋅1013 G are determined. The temperature dependence of the intensity of an atom ensemble is analyzed. 相似文献
19.
D. É. Fel’dman 《Journal of Experimental and Theoretical Physics》1999,88(6):1170-1178
The critical behavior of the transverse (with respect to the field) magnetization component in classical degenerate magnets
with only nearest-neighbors interaction in a uniaxial random magnetic field at zero temperature is found exactly. For a Gaussian
distribution of the random field the asymptotic transverse magnetization in strong fields does not depend on the dimension
of the space and is of the form m
⊥ ∝ 1nh
0/h
0
2
, where h
0 is the width of the distribution. For a bimodal distribution, where only the field direction is random and the amplitude
is fixed, the transverse magnetization behaves as m
⊥∝exp(−const/(H
c
−H)
D/2), where H is the amplitude of the random field, D is the dimension of the space, and H
c
is the critical field.
Zh. éksp. Teor. Fiz. 115, 2143–2159 (June 1999) 相似文献
20.
The effect of size on the zero field resistivity in zinc whiskers was measured. The results are in agreement withAleksandrov's value ofϱ·λ=1.8×10−11
Ωcm2. The dependence on temperature and on transverse and longitudinal magnetic field was also investigated. 相似文献