共查询到20条相似文献,搜索用时 15 毫秒
1.
Tapan Chatterji Yixi Su Yi-Cheng Lee Kannan M. Krishnan 《Journal of magnetism and magnetic materials》2010,322(21):3333-7138
We have investigated nearly monodispersive MnO nanoparticles of 10 nm diameter by polarised neutron diffraction with XYZ-polarisation analysis. We found no long-range ordering down to 3.5 K. A broad magnetic peak appeared close to Q= (1/2,1/2,1/2) signifying short-range antiferromagnetic correlations. The correlation length was found to be about 2.4 nm at T=3.5 K. The correlation length decreases rapidly with increasing temperature and becomes about 0.7 nm at T=250 K. 相似文献
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The hyperfine field on Pd nuclei in Pd-Fe alloys has been studied using the integral perturbed angular correlation technique (IPAC). Results are given for samples with iron contents from 3 to 60 at.% Fe and the temperature dependence of the hyperfine field is studied for a sample with 10 at.% Fe. 相似文献
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H. Kepa K. I. Goldman T. M. Giebultowicz C. F. Majkrzak G. Springholz H. Krenn S. Holl F. Schinagl G. Bauer 《Physica E: Low-dimensional Systems and Nanostructures》1998,2(1-4)
Neutron diffraction and magnetization studies of short-period antiferromagnetic (AF) semiconducting (1 1 1) EuTe/PbTe superlattices are presented. Due to the symmetry-breaking lattice mismatch strain, only a single AF configuration forms in the EuTe layers, instead of four allowed by symmetry in bulk EuTe. The strain and the finite layer thickness also lead to a strong shift in the Néel temperature. Neutron-diffraction spectra exhibit pronounced patterns of satellites, indicating spin correlations between successive EuTe layers separated by PbTe layers, and the transfer of magnetic interactions across the diamagnetic spaces. Experiments on samples with doped PbTe layers and in external magnetic fields rule out that the coupling is caused by any of the mechanisms known to occur in metallic superlattices. Hence, our data strongly suggest the existence of a new interlayer coupling mechanism. 相似文献
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We consider the spin-1/2 model on the honeycomb lattice [A. Kitaev, Ann. Phys. 321, 2 (2006)] in the presence of a weak magnetic field h α ? J. Such a perturbation treated in the lowest nonvanishing order over h α leads [K.S. Tikhonov, M.V. Feigel’man, and A.Yu. Kitaev, Phys. Rev. Lett. 106, 067203 (2011)] to a powerlaw decay of irreducible spin correlations 《s z (t, r)s z (0, 0)》 ∝ h z 2 f(t, r), where f(t, r) ∝ [max(t, Jr)]–4. We have studied the effects of the next order of perturbation in h z and found an additional term of the order h z 4 in the correlation function 《s z (t, r)s z (0, 0)》 which scales as h z 4 cosγ/r 3 at Jt? r, where γ is the polar angle in the 2D plane. We demonstrate that such a contribution can be understood as a result of a perturbation of the effective Majorana Hamiltonian by the weak imaginary vector potential A x ∝ i h z 2 . 相似文献
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The concentration dependence of spin waves stiffness coefficient in Pd-Fe alloys is calculated. Our results are in a good agreement with experimental results. 相似文献
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G.J. Nieuwenhuys 《Physics letters. A》1973,43(3):301-302
Results of resistivity measurements on dilute Pd-Mn alloys with concentrations from 0.15 at .% to 0.7 at .% are discussed. A calculation of the transition temperature of Pd-Co, Pd-Fe and Pd-Mn alloys with concentrations between 0.05 at .% and 3 at .% is presented and compared with the available experimental data. 相似文献
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G. V. Lecomte H. v. Löhneysen E. F. Wassermann 《Zeitschrift für Physik B Condensed Matter》1983,50(3):239-245
We report measurements of the low-field complex magnetic susceptibility on Pt1?x Mn x forx=0.01, 0.025 and 0.05 and for frequencies ν between 10 and 4,000 Hz. A strong frequency dependence of the freezing temperatureT f is observed: ΔT f /T f Δ lnv=0.025 (decade ν)?1 for all three alloys. These results as well as previous other measurements are interpreted in terms of a phenomenological model. 相似文献
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G. Ehlers C. Geibel F. Steglich H. Maletta 《Zeitschrift für Physik B Condensed Matter》1997,104(3):393-395
Neutron diffraction experiments have been performed in order to study the magnetic order of the heavyfermion compound YbNiAl. Below the Néel temperature at T N = 2.9K a sinusoidally modulated structure is found with an amplitude of the modulation of μ = (1.9±0.2)μB at T = 200 mK. The magnetic propagation vector is k m = (τ00) with τ = (0.779±0.001), and the magnetic Yb-moments are directed perpendicular to the hexagonal c-axis. The results obtained on YbNiAl are discussed in comparison to RNiAl compounds with other rare earth atoms R. 相似文献
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M. Trhlik J. Dupák B. Sedlák N. Severijns W. Vanderpoorten J. Vanhaverbeke L. Vanneste J. Wouters 《Hyperfine Interactions》1990,59(1-4):505-508
The low temperature nuclear orientation of54Mn in Pt99Fe1, Pt99,9Fe0.1 and Pt99,95Fe0.05 has been studied in the temperature rangé 5–60 mK and in the external magnetic field range 0–9 T. A considerable noncollinearity
of Mn magnetic moments with respect to Bext has been found even at rather high Bext. 相似文献
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R. M. Mirzababaev 《Physics of the Solid State》2001,43(7):1278-1282
The Mössbauer spectra of Pd-Fe films with different thicknesses and iron concentrations are measured. In these films, the spin fluctuations associated with the transition to a quasi-two-dimensional magnetic state are observed over a wide range of temperatures. The dependences of the magnetic field strength and the Curie temperature on the film thickness are quite consistent with the scaling theory. Owing to the long-range exchange coupling, the films containing 14.4 and 7.8 at. % Fe undergo a transition to the quasi-two-dimensional state at a film thickness of several thousand angströms. 相似文献
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A. G. Zabrodskii Anatoly I. Veinger T. V. Tisnek S. I. Goloshchapov 《Applied magnetic resonance》2009,35(3):439-448
A low-temperature (3–100 K) electron spin resonance (ESR) study of the spin system of neutral As donors in Ge showed that
on the insulator side of the insulator-metal transition the single-spin density exponentially disappears as T → 0. Such spins are bound into pairs to give an antiferromagnetic (AF) phase. Upon increasing the temperature the AF phase
is destroyed, the single-spin density and, as a result, the ESR absorption signal becomes stronger. The temperature dependences
of the densities of the pairs and single spins are typical for a chaotic distribution of neutral donors. In this case, there
is no Néel temperature. For a low degree of compensation, the crystal lattice of Ge with the AF phase is actually a nanostructured
system characterized by anisotropic internal stresses that are the strongest along one of the [110] directions. These stresses
give rise to the anisotropy of the g-factor which is responsible for experimentally observed splitting of the ESR line. The compensating impurities destroy the
AF phase and reduce this splitting. Local stresses are present in this case, too, but now they appear because of the Coulomb
interaction of oppositely charged impurities and have no preferred orientation. 相似文献
19.
Guo-Feng Zhang Heng Fan Ai-Ling Ji Zhao-Tan Jiang Ahmad Abliz Wu-Ming Liu 《Annals of Physics》2011,326(10):2694-2701
Bell nonlocality, entanglement and nonclassical correlations are different aspects of quantum correlations for a given state. There are many methods to measure nonclassical correlations. In this paper, nonclassical correlations in two-qubit spin models are measured by the use of measurement-induced disturbance (MID) [S. Luo, Phys. Rev. A 77 (2008) 022301] and geometric measure of quantum discord (GQD) [B. Daki?, V. Vedral, C. Brukner, Phys. Rev. Lett. 105 (2010) 190502]. Their dependences on external magnetic field, spin–spin coupling, and the Dzyaloshinskii–Moriya (DM) interaction are presented in detail. We also compare Bell nonlocality, entanglement measured by concurrence, MID and GQD and illustrate their different characteristics. 相似文献
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57Fe Mössbauer measurements on the reentrant spin glass system (Fe .65 Ni .35)1?x Mn x are analysed under the extreme assumption that only relaxation determines the shape of the spectra. A plain model of a fluctuating hyperfine field based on the Blume-Tjon-theory /1/ is used for the evaluation. As a result the increase of the fluctuation frequencies with increasing temperature yields in lowering of the relative magnetization. Noticeable are some typical kinks of the magnetization at the reentrant temperatures. Our evaluation results in fluctuation frequencies from 107 Hz to 109 Hz, which indicates, if true, that the reason of the fluctuations seems not to be single spins but larger collective spin groups (clusters). 相似文献