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41.
The influence of thermal fluctuations on magnetization-reversal processes in ultrathin magnetic particles is investigated
on the basis of a numerical solution of the Landau-Lifshitz-Gilbert equations taking account the thermal-activation fluctuation
field. It is shown that for nanoparticles there exists a region of magnetic and geometric parameters where a strong jump-like
instability of the critical field for magnetization reversal arises. This instability is due to the thermally activated transformation
of magnetization configurations far from the switching threshold. The thermal-instability mechanism described is important
for particles of much larger sizes than for the single-mode Néel-Brown instability.
Pis’ma Zh. éksp. Teor. Fiz. 69, No. 8, 555–560 (25 April 1999) 相似文献
42.
D. A. Balaev S. I. Popkov A. A. Krasikov A. D. Balaev A. A. Dubrovskiy S. V. Stolyar R. N. Yaroslavtsev V. P. Ladygina R. S. Iskhakov 《Physics of the Solid State》2017,59(10):1940-1946
The cross-breeding problem of the temperature dependence of the antiferromagnetic susceptibility of ferrihydrite nanoparticles is considered. Iron ions Fe3+ in ferrihydrite are ordered antiferromagnetically; however, the existence of defects on the surface and in the bulk of nanoparticles induces a noncompensated magnetic moment that leads to a typical superparamagnetic behavior of ensemble of the nanoparticles with a characteristic blocking temperature. In an unblocked state, magnetization curves of such objects are described as a superposition of the Langevin function and the linear-in-field contribution of the antiferromagnetic “core” of the nanoparticles. According to many studies of the magnetization curves performed on ferrihydrite (and related ferritin) nanoparticles in fields to 60 kOe, dependence χAF(T) decreases as temperature increases, which was related before to the superantiferromagnetism effect. As the magnetic field range increases to 250 kOe, the values of χAF obtained from an analysis of the magnetization curves become lower in magnitude; however, the character of the temperature evolution of χAF is changed: now, dependence χAF(T) is an increasing function. The latter is typical for a system of AF particles with random orientation of the crystallographic axes. To correctly determine the antiferromagnetic susceptibility of AF nanoparticles (at least, ferrihydrite) and to search for effects related to the superantiferromagnetism effect, it is necessary to use in experiments the range of magnetic field significantly higher than that the standard value 60 kOe used in most experiments. The study of the temperature evolution of the magnetization curves shows that the observed crossover is due to the existence of small magnetic moments in the samples. 相似文献
43.
44.
Kulagin N. E. Popkov A. F. Solov’yov S. V. Zvezdin A. K. 《Physics of the Solid State》2019,61(2):108-116
Physics of the Solid State - Alterations in the ground state of thin (001) films of a BiFeO3 (BFO)-type multiferroic in a magnetic field are studied theoretically, with changes in the energy of... 相似文献
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49.
Marina S. Fonari Yurii A. Simonov Victor Ch. Kravtsov Vladimir O. Gelmboldt Edward V. Ganin Yurii A. Popkov Larisa V. Ostapchuk 《Journal of inclusion phenomena and macrocyclic chemistry》1998,30(3):197-213
Novel complementary associations have been found in a crystalline ternarycomplex of the macrocyclic tetramine, [12]aneN4 (e.g. =1,4,7,10-tetraazacyclododecane, cyclen, L), hexafluorosilicate ions andwater (I). The final compound belongs to the host—guest type with themacrocycle as the host (H), the inorganic entity as a guest (G) and watermolecules. It was characterized by X-ray techniques, IR spectroscopy andthermogravimetric study. X-ray crystal analysis revealed that the structureis built of the charged entities, with a 3D-network uniting thequadriprotonated form of the macrocycle, hexafluorosilicate as counterionsand lattice water molecules viaN—H+...F-,N—H+...O(w),OH...F- and O—-H(w)...O(w)hydrogen bonds. The overall complex stoichiometry comprises fourSiF6
2- anions and seven water molecules per two[LH4]4+ cations. Crystals of (I) are monoclinic,space group P21/n with a = 14.585(3), b = 16.384(2), c =16.500(3) Å, = 92.84(3)°, V = 3938(1)Å3 and Z = 8 forC8H31F12N4O3.5Si2. 相似文献
50.
Yu. N. Belokon' N. I. Chernoglazova E. V. Ivanova A. N. Popkov M. B. Saporovskaya N. N. Suvorov V. M. Belikov 《Russian Chemical Bulletin》1988,37(12):2541-2544
Conclusions The synthesis of optically pure S-5-benzyloxytryptophan, S--(2-naphthyl)alanine, and S--allylglycine was carried out by alkylating glycine in the Ni(II) complex of its Schiff base with S-2-N-(N-benzylpropyl)aminobenzophenone, followed by Chromatographic separation of the mixture of diastereomeric alkylated complexes.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 12, pp. 2818–2821, December, 1988. 相似文献