We have carried out measurements of domain wall dynamics in a Pt/Co/GdOx(t) wedge sample with perpendicular magnetic anisotropy. When driven by an easy-axis field Hz in the presence of an in-plane ...field Hx, the domain wall propagation is different along x, as expected for samples presenting Dzyaloshinskii-Moriya (DMI) interaction. In the creep regime, the sign and the value of the domain wall velocity asymmetry changes along the wedge. We show that in our samples the domain wall speed versus Hx curves in the creep regime cannot be explained simply in terms of the variation of the domain wall energy with Hx, as suggested by previous works. For this reason the strength and the sign of the DMI cannot be extracted from these measurements. To obtain reliable information on the DMI strength using magnetic field-induced domain wall dynamics, measurements have been performed with high fields, bringing the DW close to the flow regime of propagation. In this case we find large values of the DMI, consistent in magnitude and sign with those obtained from Brillouin light scattering measurements.
Modern spectroscopic techniques for the investigation of magnetization dynamics in micro- and nano- structures or thin films use typically microwave antennas which are directly fabricated on top of ...the sample by means of electron-beam-lithography (EBL). Following this approach, every magnetic structure on the sample needs its own antenna, resulting in additional EBL steps and layer deposition processes. We demonstrate a new approach for magnetization excitation that is suitable for optical and non-optical spectroscopy techniques. By patterning the antenna on a separated flexible glass cantilever and insulating it electrically, we solved the before mentioned issues. Since we use flexible transparent glass as a substrate, optical spectroscopy techniques like Brillouin-light-scattering microscopy ({\mu}BLS), time resolved magneto-optical Kerr effect measurements (TRMOKE) or optical detected magnetic resonance (ODMR) measurements can be carried out at visible laser wavelengths. As the antenna is detached from the sample it can be freely positioned in all three dimensions to adress only the desired magnetic sample structures and to achieve effective excitation. We demonstrate the functionality of these antennas using {\mu}BLS and compare coherently and thermally excited magnon spectra to show the enhancement of the signal by a factor of about 400 due to the excitation by the antenna. Moreover, we succeed to characterize yttrium iron garnet thin films with spatial resolution using optical ferromagnetic resonance (FMR) experiments. We analyse the spatial excitation profile of the antenna by measuring the magnetization dynamics in two dimensions. The technique is furthermore applied to investigate injection-locking of spin Hall nano-oscillators.
We carried out measurements of domain wall (DW) velocities driven by magnetic field pulses in symmetric Pt/Co/Pt and asymmetric Pt/Co/AlOx, Pt/Co/GdOx and Pt/Co/Gd trilayers with ultrathin Co layers ...and perpendicular magnetic anisotropy. In agreement with theoretical models, the maximum observed velocity is much larger in the asymmetric samples, where the interfacial Dzyaloshinskii-Moriya interaction (DMI) stabilises chiral Néel walls, than in the symmetric stack. In addition, in Pt/Co/Gd very large DW speeds (up to 600 m/s) are obtained, 2.5 times larger than in samples with oxidised Gd. Magnetic measurements reveal that this may be explained by the anti-parallel coupling between the magnetic moments of Gd and Co at the Gd/Co interface, leading to a decrease of the total magnetisation. In quantitative agreement with analytical models, in all samples the maximum observed DW speed scales as D=Ms, where D is the strength of the DMI and Ms the spontaneous magnetisation.
We have carried out measurements of domain wall dynamics in a Pt/Co/GdOx(t) wedge sample with perpendicular magnetic anisotropy. When driven by an easy-axis field Hz in the presence of an in-plane ...field Hx, the domain wall expansion along x is anisotropic, as expected for samples presenting Dzyaloshinskii-Moriya interaction. In the creep regime, the sign and the value of the domain wall velocity asymmetry changes along the wedge. We show that in our samples the domain wall speed vs. Hx curves in the creep regime cannot be explained simply in terms of the variation of the domain wall energy with Hx, as suggested by previous works. For this reason the strength and the sign of the Dzyaloshinskii-Moriya interaction (DMI) cannot be extracted from these measurements. To obtain reliable information on the DMI strength using magnetic field-induced domain wall dynamics, measurements have been performed with high fields, bringing the DW close to the flow regime of propagation. In this case, the large values of DMI are coherent with those obtained from current-driven domain wall dynamics.
The descent and localization of eggs and embryos in individual segments of the reproductive tract of superovulated cows were studied in this work. For the induction of superovulation, serum ...gonadotropin (PMSG, Ivanovice in Haná) at a dose of 2,500-3,500 I.U. was used, in combination with 0.5 mg of Cloprostenol (Oestrophan, Spofa), administered 48 hours after gonadotropin treatment. The start of superovulation fell on days 9 to 12 of the sexual cycle and was conditioned by the presence of the corpus luteum (CL). After the onset of the heat, 2-3 inseminations were carried out using fresh semen. Donor cows were slaughtered 3, 4, 5, 6, and 7 days after the second insemination and isolated reproductive organs (Fig. 1) were divided into five segments (two on oviducts and three on uterine horns) by the applied ligature. In laboratory conditions superovulation response was determined accurately, the volume of ovaries was assessed according to water displacement and the segments of oviducts and uterus were rinsed with TCM 199 or PBS supplemented with FCS. 3, 4, 5, 6, and 7 days after insemination (Tab. I). 18.1 (+/- 3.55), 12.4 (+/- 0.91), 19.2 (+/- 2.86), 20 and 23 (+/- 2.44) CL on average were recorded, which corresponded to the ovulation of 64, 50, 56, 71 and 72 percent of stimulated follicles (Fig. 2). Within 3 to 7 days after insemination nearly triple enlargement of ovaries was also observed (Tab. I, Fig. 3). During the lavage of individual segments of the tubular reproductive tract, 38 per cent of eggs and embryos were detected in the uterus as early as 3 days after insemination (Tab. II). Unfertilized eggs and degenerated embryos were found in the 2nd and 3rd uterine segment, embryos at the stage of 8-16 blastomeres were localized in the 1st and 2nd segment of the uterus. Four days after insemination (Tab. III), about 64 per cent of eggs and embryos at the stage up to 16 blastomeres were found in the uterus, but embryos up to 32 blastomeres were still flushed out of the oviduct. On day 5 after insemination, 92 per cent of eggs and embryos were released into the uterus, being localized mostly in the cranial and medial part of the uterus (Tab. IV). 7.5 per cent of recovered eggs and embryos at the stage of early or compacted morulae were still detected in the oviducts.
Postmortem statistics of veterinary practice does not present data on deaths in domestic animals caused by a disorderly clotting, i.e. by the varying degree of clotting and embolic complications. A ...clinical evaluation of their frequency is difficult owing to mild symptoms in the majority of cases, so that the presence of a thrombus can be proved only after extensive examinations. In severe cases the complications are manifested rather dramatically and mostly followed by a lethal outcome. Erythrocyte count was made in Neubauer chamber; thrombocytes were evaluated according to the method of Foni: haematocrit was determined using micromethod; haemoglobin and prothrombin time were determined according to Sahli and Quick, respectively. Bleeding and clotting times and coagulum retraction were also determined. In a certain, however, limited number of cases, the results have suggested disorders of the clotting mechanism.
Prenos embryi u skotu nekrvavou cestou v podminkach velkovyroby Holy, L; Jiricek, A; Vanatka, F ...
Zivocisna vyroba - Ceskoslovenska akademie zemedelska, Ustav vedeckotechnickych informaci pro zemedelstvi,
1984, Letnik:
29, Številka:
10
Journal Article
PDF
