Induced Anisotropies in NiCo Obliquely Deposited Films and Their effect on Magnetic Domains

English Article: Oblique and in-plane anisotropies in obliquely evaporated NiCo thin films were investigated in order to understand their origin. All the compositions studied clearly show the effect of columnar grain morphology coupled with some intrinsic factors such as magnetostriction and crystallinity. Energy calculations are undertaken to explain the effect of

Fluctuations and Instabilities of Ferromagnetic Domain Wall pairs in an External Magnetic Field

Soliton excitations and their stability in anisotropic quasi-1D ferromagnets are analyzed analytically. In the presence of an external magnetic field, the lowest lying topological excitations are shown to be either soliton-soliton or soliton-antisoliton pairs. In ferromagnetic samples of macro- or mesoscopic size, these configurations correspond to twisted or untwisted pairs of Bloch walls. It is shown that the fluctuations around these configurations are governed by the same set of operators. The soliton-antisoliton pair has exactly one unstable mode and thus represents a critical nucleus for thermally activated magnetization reversal in effectively one-dimensional systems. The soliton-soliton pair is stable for small external fields but becomes unstable for large magnetic fields. From the detailed expression of this instability threshold and an analysis of nonlocal demagnetizing effects it is shown that the relative chirality of domain walls can be detected experimentally in thin ferromagnetic films. The static properties of the present model are equivalent to those of a nonlinear sigma-model with anisotropies. In the limit of large hard-axis anisotropy the model reduces to a double sine-Gordon model.Comment: 15 pages RevTex 3.0 (twocolumn), 9 figures available on request, to appear in Phys Rev B, Dec (1994

Deposition of Ru-106 and I-125 on silver by internal electrolysis

The application of internal electrolysis for the deposition of ruthenium-106 and iodine-125 on silver was examined. These investigations were aimed at the preparation of sealed radiation sources for brachytherapy. The current and voltage of a cell built of silver cathode and aluminium anode, immersed in electrolytes containing different concentrations of ruthenium were determined. The same parameters were measured for the cell consisting of silver anode and platinum cathode as a function of the concentrations of NaI and NaOH in the electrolyte. The changes of current and voltage of the cells as a function of duration of electrolysis were investigated. The influence of white light observed during the deposition of iodine indicates that photolysis of silver iodide formed on the anode affects the cell parameters. From the results obtained it follows that electrolysis performed without application of external electric tension is a simple and convenient method for fixing considerable amounts of both ruthenium-106 and iodine-125 on silver

MAGNETIC STRUCTURE IN OBLIQUELY DEPOSITED Co-Au FILMS

Les couches minces de Co-Au de différentes compositions, déposées obliquement sous incidence de 40° et 60°, ont été étudiées. Les couches se caractérisent par un facteur de qualité Q > 1 ; les domaines en rubans "forts" se manifestent dans tous les échantillons ; les rubans faibles ont aussi pu être observés dans quelques couches déposées sous l'angle 40°.The magnetic properties and domain structure of Co-Au films of various compositions, deposeted at angles of incidence of 40° and 60° have been studied. Values of Q ranged from just under to well over 1. Strong stripe domains were obdserved in all specimens. Some specimens contained weak stripe domains as well

DOMAIN TIPS : STRUCTURE AND MOBILITY IN UNIAXIAL AMORPHOUS THIN FILMS

Statics and dynamics of domain tips have been investigated by high resolution Kerr effect using digital contrast enhancement. The magnetic structure is affected by demagnetizing effect. The internal wall structure is visible and a transition between asymmetric Bloch wall to Néel one is shown. Tip propagation along the easy axis is measured

Radiation Environment at Aviation Altitudes and in Space

On the Earth, protection from cosmic radiation is provided by the magnetosphere and the atmosphere, but the radiation exposure increases with increasing altitude. Aircrew and especially space crew members are therefore exposed to an increased level of ionising radiation. Dosimetry onboard aircraft and spacecraft is however complicated by the presence of neutrons and high linear energy transfer particles. Film and thermoluminescent dosimeters, routinely used for ground-based personnel, do not reliably cover the range of particle types and energies found in cosmic radiation. Further, the radiation field onboard aircraft and spacecraft is not constant; its intensity and composition change mainly with altitude, geomagnetic position and solar activity (marginally also with the aircraft/spacecraft type, number of people aboard, amount of fuel etc.). The European Union Council directive 96/29/Euroatom of 1996 specifies that aircrews that could receive dose of >1 mSv y(-1) must be evaluated. The dose evaluation is routinely performed by computer programs, e.g. CARI-6, EPCARD, SIEVERT, PCAire, JISCARD and AVIDOS. Such calculations should however be carefully verified and validated. Measurements of the radiation field in aircraft are thus of a great importance. A promising option is the long-term deployment of active detectors, e.g. silicon spectrometer Liulin, TEPC Hawk and pixel detector Timepix. Outside the Earth\u27s protective atmosphere and magnetosphere, the environment is much harsher than at aviation altitudes. In addition to the exposure to high energetic ionising cosmic radiation, there are microgravity, lack of atmosphere, psychological and psychosocial components etc. The milieu is therefore very unfriendly for any living organism. In case of solar flares, exposures of spacecraft crews may even be lethal. In this paper, long-term measurements of the radiation environment onboard Czech aircraft performed with the Liulin since 2001, as well as measurements and simulations of dose rates on and outside the International Space Station were presented. The measured and simulated results are discussed in the context of health impact