Magnetoelectric coupling and spin-canting in FeCr<inf>2</inf>O<inf>4</inf> ferrimagnet

Within the framework of the quantum mechanical approach, the microscopic theory for magnetoelectric coupling and spin-canting in the spin ordered FeCr2O4 is discussed. We describe two possible mechanisms of magnetoelectric coupling caused by the combined action of the odd crystal field from the tetrahedral environment of the iron ions, the spin–orbit interaction and the exchange field acting on the 3d iron electrons from the chromium spins. We also consider sources of spin-canting. The first one is DM interaction which induces an angle-canting about 2°, the second is a new one due to the common action of the Jahn–Teller and spin–orbit couplings, which yields up to the 50°

Even and odd crystal fields on Fe²⁺ions, local lattice distortion parameters, electron-deformation interaction, and magnetoelectric coupling in FeCr<inf>2</inf>O<inf>4</inf>

Within the framework of the quantum mechanical approach, the available experimental data are analyzed to identify the electronic structure of the multiferroic FeCr2O4. The relative values of the key contributions to the parameters of even and odd crystal fields acting on the 3d electrons of the Fe2+ ion are determined. Data on local lattice distortions are systematized. The parameter of the electron-deformation interaction of the ground term Fe2+ (5 E) is determined considering lattice distortions, and the parameters of binding of the spins of Fe2+ and Cr3+ to the electric field are estimated. The calculation results are compared with the available experimental data on the magnetic and structural characteristics of FeCr2O4, the critical temperature of the transition to an orbitally ordered state, optical conductivity data, the Mössbauer effect study, and measurements of spontaneous electric polarization

Morphologic structure and immunohistochemical analysis of vaginal wall in women with pelvic organ prolapse

AIM: to study a correlation between clinical stage of pelvic organ prolapse (POP), a histological structure and results of immunohistochemical study of the vaginal wall were evaluated. MATERIALS AND METHODS: A total of 60 peri- and postmenopausal women (average age 61.9+/-8.4 years) with POP of stage II-IV, according to the POP-Q classification, or with stress urinary incontinence and cystocele of stage I-II, who undergone to surgical treatment, were included in the study. During a procedure, a biopsy from the anterior vaginal wall was taken. Depending on the stage of POP, patients was divided into two groups. In the group 1, 30 patients with stage I and II of POP were included, while group 2 included 30 women with POP of stage III and more. The control group (group 3) consisted of 20 patients without POP (mean age 63.4+/-11.0 years) who underwent a hysterectomy due to to other indications. A histological and immunohistochemical studies of vaginal wall tissue was performed in order to determine the tissue content of collagen type I and III; matrix metalloproteinases 1 and 2 (MMP-1 and MMP-2), a tissue inhibitor of metalloproteinases 1 (TIMP-1), vimentin and smooth muscle actin. RESULTS: In contrast to two other groups, in group 2 there were significant changes in the connective tissue. Collagen has a form of fibrous mass with areas of reduced content. In addition, scarring areas with an increase in the content of type III collagen, a decrease in the amount of type I collagen and elastic fibers with significant fragmentation, were seen. Moreover, in patients with severe POP (III-IV), degradation of collagen fibers with a decrease in connective tissue strength and elasticity was detected. Women with POP had a low ratio of type I:III collagen. Analysis of the collagen content in the vaginal wall in patients with mild POP (I-II) revealed a significant increase in the level of collagen type I (p=0.0003) and a decrease in the content of type III (p=0.045), compared to patients with more severe POP (III-IV). The level of MMP-1 and MMP-2 in women with POP was higher, than in control group by 1.7 times (p<0.05). The content of TIMP-1 in the group 1 was significantly lower by 1.5 and 2.2 times, compared to group 2 and 3, respectively. An analysis of MMP-1 and MMP-2 concentration in patients of groups 1 and 2 revealed a significant (p=0.04) decrease in their activity in severe POP (III-IV). In women of the group 2, biopsy of the vaginal wall showed that expression of vimentin and smooth muscle actin in the connective tissue was significantly higher, than in group 1 and 3 (p<0.05). Vimentin expression in the group 2 was 1.4 and 2.6 times higher than in the group 1 and 3, respectively. In the control group, the expression of these markers in the vaginal wall was minimal and focal. CONCLUSION: Our data indicate that fibrosis and degradation of the connective tissue in the vaginal wall predominate in POP, and these changes are a consequence, but not a cause of PG. The aggravation of degenerative changes in the connective tissue leads to the progression of POP

Investigation of low-coherence laser radiation interaction with different materials

The paper presents the results of experiments on the interaction of low-coherence laser radiation with low density volume-structured materials and solid-state density materials, performed at the facility “KANAL-2” [1]. The data on scattering, absorption, and transport of low-coherence heating laser radiation through plasmas from low-density volume-structured materials and solid density materials have been analyzed. The experiments have demonstrated that laser radiation of low coherence effectively interacts with low density materials, and materials of solid-state density

Magnetoelectric properties and low-energy excitations of multiferroic FeCr2 S4

© 2020 American Physical Society. We report on the low-frequency optical excitations in the multiferroic ground state of polycrystalline FeCr2S4 in the frequency range 0.3-3 THz and their changes upon applying external magnetic fields up to 7 T. In the ground state below the orbital-ordering temperature TOO=9 K we observe the appearance of several new modes. By applying the external magnetic field parallel and perpendicular to the propagation direction of the THz radiation, we can identify the strongest absorptions to be of predominantly electric-dipole origin. We discuss these modes as the low-energy electronic excitations of the Fe2+ ions (3d6, S=2) in an tetrahedral S2- environment. The eigenfrequencies and relative intensities of these absorption lines are satisfactorily reproduced by our calculation assuming an effective exchange field of 12.8cm-1 at the Fe2+-ions sites. The direction of the exchange field is found to be slightly tilted out of the ab plane. With our approach we can also describe previously reported results from Mössbauer studies and the order of magnitude of the electric polarization induced by orbital and noncollinear spin ordering

Surface Machining of Corundum-Ceramic Components by Free Abrasive

© 2020, Allerton Press, Inc. Abstract: The surface machining of corundum-ceramic components by free abrasive is discussed. The influence of the following factors on the final surface roughness is determined: the type of machining (tumbling or vibrational tumbling), the shape of the abrasive bodies, the presence or absence of machining fluid, the machining time, and the drum speed in tumbling. On that basis, recommendations are presented