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21.
R. F. Mamin 《Bulletin of the Russian Academy of Sciences: Physics》2007,71(10):1362-1364
The influence of defects with changing properties on the characteristics of structural phase transitions has been theoretically investigated. The effect of repolarizing defects on the dielectric susceptibility and the dynamics of the order parameter has been studied and the temperature dependences of these characteristics have been obtained. The contribution of the defect states to the formation of a diffuse phase transition with dispersion at low frequencies is discussed. 相似文献
22.
We have used the large gradients generated near the ferromagnetic tip of a magnetic resonance force microscope to locally suppress spin diffusion in a silica sample containing paramagnetic electron spins. By controlling the slice location with respect to the tip, the magnetic field gradient was varied from 0.01 to 36 mT/microm, resulting in a fourfold decrease in T-11 and a similar decrease in T(-1)(1 rho). The observed dependence of the relaxation rates on field gradient is consistent with the quenching of flip-flop interactions that mediate the transport of magnetization between slow and fast relaxing spins. 相似文献
23.
Cantilever magnetometry with moment resolution better than 10(4)micro(B) was used to study individual nanomagnets. By using the fluctuation-dissipation theorem to interpret measurements of field-induced cantilever damping, the low frequency spectral density of magnetic fluctuations could be determined with resolution better than 1micro(B) Hz-1/2. Cobalt nanowires exhibited significant magnetic dissipation and the associated magnetic fluctuations were found to have 1/f frequency dependence. In individual submicron rare-earth alloy magnets, the dissipation/fluctuation was very small and not distinguishable from that of a bare silicon cantilever. 相似文献
24.
Noncontact friction between a Au(111) surface and an ultrasensitive gold-coated cantilever was measured as a function of tip-sample spacing, temperature, and bias voltage using observations of cantilever damping and Brownian motion. The importance of the inhomogeneous contact potential is discussed and comparison is made to measurements over dielectric surfaces. Using the fluctuation-dissipation theorem, the force fluctuations are interpreted in terms of near-surface fluctuating electric fields interacting with static surface charge. 相似文献
25.
Marat Gafurov Timur Biktagirov Georgy Mamin Sergei Orlinskii 《Applied magnetic resonance》2014,45(11):1189-1203
Incorporation of the nitrogen-containing impurities in hydroxyapatite (HAp) powders with the sizes of the crystallites of (20–50) nm was studied using first-principles modeling combined with the multi-frequency (9 and 94 GHz) electron paramagnetic resonance (EPR) methods. It is shown that the observed EPR spectra are undoubtedly due to the presence of the bulk radiation-induced NO3 2? radicals. This conclusion is based on spin-polarized density functional theory calculations of spectroscopic parameters within gauge-including projector augmented wave framework followed by the exact comparison of the simulated EPR and electron–nuclear double resonance spectra with the experimental findings. In addition, a comprehensive analysis of the simulated properties allows us to suggest that the paramagnetic centers preferably occupy PO4 3? sites in the HAp structure. 相似文献
26.
E. G. Il’in A. V. Rotov A. S. Parshakov N. N. Efimov E. A. Ugolkova G. V. Mamin S. B. Orlinskii V. V. Minin 《Russian Journal of Inorganic Chemistry》2013,58(2):183-185
The organo-inorganic composite MoCl1.9 ± 0.1(C30 ± 1H30 ± 1), a product of interaction of MoCl5 with C2H2, has been studied by X- and W-band EPR, double electron nuclear resonance, and W-band electron spin echo spectroscopy. The composite consists of nanosized organometallic molybdenum clusters in the polyacetylene matrix. It has been shown that the composite contains three types of magnetic centers: the first is related to the existence of paramagnetic molybdenum atoms in the polyacetylene matrix, and the other two are paramagnetic defects of the matrix. 相似文献
27.
R. F. Mamin D. A. Tayurskii 《Bulletin of the Russian Academy of Sciences: Physics》2016,80(9):1042-1045
A phenomenological model is proposed for describing the behavior of ferroelectrics with the diffuse phase transition near the permittivity maximum in the low-temperature phase. The behavior in this temperature range is shown to be related to the dynamics of formation of polarized state regions near defects with localized charges. The delay in the transition to the uniformly polarized state in the low-temperature phase is discussed. 相似文献
28.
Yavkin BV Mamin GV Orlinskii SB Gafurov MR Salakhov MKh Biktagirov TB Klimashina ES Putlayev VI Tretyakov YD Silkin NI 《Physical chemistry chemical physics : PCCP》2012,14(7):2246-2249
W-band pulsed EPR and ENDOR investigations of X-ray irradiated nanoparticles of synthetic hydroxyapatite Ca(9)Pb(PO(4))(6)(OH)(2) are performed. It is shown that in the investigated species lead ions probably replace the Ca(1) position in the hydroxyapatite structure. 相似文献
29.
A. A. Bush K. E. Kamentsev R. F. Mamin 《Journal of Experimental and Theoretical Physics》2005,100(1):139-151
The special features of the dielectric properties and conduction of ferroelectric crystals of Pb5(Ge1?xSix)3O11 (0 ≤ x ≤ 0.67) solid solutions were studied. Permittivity anomalies close to the temperatures T1 ≈ 260 K and T2 ≈ 130 K, the appearance of relaxator behavior at x > 0.35, and critical behavior of the concentration dependences of dielectric and pyroelectric characteristics at x1 = 0.35 and x2 = 0.60 were observed and studied. These phenomena were found to be related to the dynamics of charge localization on defects with activation energies of Ua1 ≈ 0.6 eV and Ua2 ≈ 0.23 eV. Relaxator behavior appears when the Curie point lies in the temperature region of thermal charge localization. The concentration dependence features at x1 and x2 are explained by the coincidence of the Curie point and the centers of the temperature regions of charge localization on the Ua1 and Ua2 defect levels, respectively. 相似文献
30.