Csatolási, anizotrópia és domén-jelenségek mágneses vékonyrétegekben = Coupling, anisotropy and domain phenomena in magnetic thin films

Antiferromágnesesen (AF) csatolt fémes multirétegek fontos szerepet játszanak mind az alapkutatásban, mind a mágneses adatrögzítésben és szenzorikában. A projekt célja volt egyes, az óriás mágneses ellenállás (GMR) jelenségén alapuló nanoeszközök teljesítőképességét befolyásoló csatolási és mágneses anizotrópia tulajdonságok, valamint mágneses doménjelenségek felderítése. Kísérleti módszereink a mágnesezettség és a mágneses ellenállás mérése, a neutronreflektometria, a szinkrotron-Mössbauer-reflektometria (SMR) és a Mössbauer-polarimetria voltak. A projekt főbb eredményei: Azonosítottuk a szuperparamágneses tartományok GMR-járulékát elektrolitikusan leválasztott Co/Cu multirétegekben, módszert dolgoztunk ki annak elkülönítésére és minimalizálására. Felderítettük az AF-domének érésének mechanizmusát erősen csatolt Fe/Cr multirétegekben, igazoltuk abban a koercitív erő szerepét. A "túltelítési doménmemória-hatást" a réteg-réteg-csatolás laterális eloszlásával magyaráztuk. Két új doménátalakulást, a hőmérsékletindukált érést és a komplex durvulást találtuk meg és elemeztük. Kifejlesztettük az érés Monte Carlo-szimulációját és általános sejtautomata-modelljét. Megalkottuk a diffúz SMR teljes DWBA-elméletét és -algoritmusát. Kidolgoztuk a laboratóriumi és a szinkrotronos vékonyréteg-Mössbauer-polarimetria elveit és a módszereket Fe/Cr és Fe/Gd multirétegek csatolási tulajdonságainak vizsgálatára alkalmaztuk. Megépítettük és beüzemeltük a világ első CEMS polarimétereit. | Antiferromagnetically (AF) coupled metallic multilayers play an important role in fundamental science as well as in magnetic recording technology and sensorics. The project aimed at clarifying coupling and magnetic anisotropy properties and also magnetic domain phenomena influencing the performance of nanodevices based on giant magnetoresistance (GMR). Experimental methods included measurement of magnetisation and magnetoresistance, neutron reflectometry, synchrotron Mössbauer reflectometry (SMR) and Mössbauer polarimetry. Main results of the project: GMR contribution of superparamagnetic regions in electrodeposited Co/Cu multilayers was identified; a method was developed for separating and minimising it. The mechanism of ripening of AF domains in strongly-coupled Fe/Cr multilayers was elucidated and the role of coercivity was demonstrated. 'Supersaturation memory effect' was ascribed to lateral distribution of the layer-layer coupling. Two new domain transformations, viz. temperature-induced ripening and complex coarsening were found and analysed. A Monte Carlo simulation and a general cellular automaton model of ripening were developed. Full DWBA theory and algorithm of diffuse SMR were established. Principles of laboratory and synchrotron thin-film Mössbauer polarimetry were elaborated and the methods were applied to studying coupling properties of Fe/Cr and Fe/Gd multilayers. The world's first CEMS polarimeters were built and put into operation

On the microscopic origin of the magneto-electronic phase separation in Sr doped LaCoO3

The nanoscopic magneto-electronic phase separation in doped La1-xSrxCoO3 perovskites was studied with local probes. The phase separation is directly observed by M\"ossbauer spectroscopy in the studied doping range of 0.05 <= x <= 0.25 both at room-temperature as well as in the low temperature magnetic phase. Extended with current synchrotron based X-ray spectroscopies, these data help to characterize the volume as well as the local electric and magnetic properties of the distinct phases. A simple model based on a random distribution of the doping Sr ions describes well both the evolution of the separated phases as well as the variation of the Co spin state. The experiments suggest that Sr doping initiates small droplets and a high degree of doping driven cobalt spin-state transition, while the Sr-free second phase vanishes rapidly with increasing Sr content

Angular dependence, blackness and polarization effects in integral conversion electron Mössbauer spectroscopy

Abstract General expressions of the electron yield in 57Fe integral conversion electron Mössbauer spectroscopy were derived depending on the glancing angle of the γ photons, on the source polarization and on the isotopic abundance of the source and the absorber (blackness effects) using an exponential escape function of the electrons originating from all Mössbauer-resonance-related processes. The present approach provides a firm theoretical basis to determine the alignment and direction of magnetization in the absorber. The intensity formulae were justified by least squares fits of α-57Fe spectral intensities measured in linearly and elliptically polarized source and absorber geometries. The fits reproduce the experimentally set angles with high accuracy. Limits of the current approach and its relation to other, less complete treatments in the literature are discussed

A Three-Dimensional Analysis of Magnetic Nanopattern Formation in FeRh Thin Films on MgO Substrates: Implications for Spintronic Devices

Magnetic nanopatterns were successfully created in FeRh thin film deposited on MgO (100) substrates. Silica and polystyrene spherical masks, nominally 500 and 1000 nm in diameter, respectively were applied on the surface of the sample in order to locally shadow the film against the effect of 110 keV energy neon-ion irradiation with fluences of 10 15 and 10 16 ions/ cm2 . Such nanosphere-lithography technique allows for projecting the mask geometry on the magnetic structure of the FeRh film. Conversion-electron Mö ssbauer spectroscopy and magnetic force microscopy were used to determine the ferromagnetic ratio and the magnetic pattern in the samples, and nuclear resonance scattering of synchrotron radiation was applied to obtain the in- depth magnetic profile. From the results obtained, the possible three-dimensional (3D) structure of the created individual magnetic domains was also constructed. Overall, the great customizability of the presented nanosphere-lithography technique in FeRh thin film provides opportunities for developing cutting-edge spintronic applications

Correlation between Heavy Metal-Induced Histopathological Changes and Trophic Interactions between Different Fish Species

This study assessed the distribution of heavy metals in the gills, kidney, and liver, correlated with the severity of histopathological changes, of three fish species with different feeding habitats (Barbus barbus, Squalius cephalus, and Chondrostoma nasus) from the Crisul Negru river, Romania. The levels of copper (Cu), chromium (Cr), cadmium (Cd), lead (Pb), and zinc (Zn) in fish tissues were measured by atomic absorption spectrophotometry. Histopathology and the expressions of TNF-alpha and proliferation cell nuclear antigen (PCNA) were investigated by immunohistochemistry and Western blot. Our data suggest a significant correlation between the bioconcentration level of metals and structural changes. The carnivorous species was the most affected compared to the omnivorous and herbivorous ones, and the most affected organ was the kidney. Moreover, the correlation of tissue damage with the PCNA and TNF-alpha expression levels revealed that the herbivorous species presented less extended lesions, likely due to higher activated repair mechanisms and lower levels of inflammation. In conclusion, our data and the subsequent statistical analysis suggest that feeding behavior could be correlated with the histopathological alterations and might be used for a more profound evaluation of aquatic environment safety and analysis of aquatic ecosystems

Synergy effect of temperature, electric and magnetic field on the depth structure of the FeRh/BaTiO3 composite multiferroic

FeRh based composite multiferroic materials have attracted great scientific interest due to their wide variety of possible applications in future nano device technology. In the recent work, a comprehensive study on the depth dependence of the metamagnetic phase transition in FeRh/BaTiO3 heterostructure is reported by means of single or combined external stimulus such as heat, magnetic or electric field. Grazing-incidence nuclear scattering experiments revealed significant discrepancies in the mechanism of the antiferromagnetic/ferromagnetic reor- dering induced by the different effects, with distinguished role of both upper and lower interfaces

Magyar Tanítóképző 10 (1895) 01

Magyar Tanítóképző A Tanítóképző-intézeti Tanárok Országos Egyesületének közlönye 10. évfolyam, 01. füzet Budapest, 1895. január h

ST-elevációval járó akut szívizominfarktus miatt kórházba felvett betegek halálozása a szívkatéteres labor megnyitása előtt és után Szombathely városban = Mortality of patients admitted to hospital with acute ST-elevation myocardial infarction, before and after the opening of primary percutaneous coronary intervention unit in Szombathely

Az akut szívizominfarktus kezelési stratégiája alapvetően megváltozott az elmúlt időszakban. Továbbra is vita tárgya a két reperfúziós stratégia, a primer percutan coronariaintervenció és a fibrinolízis összehasonlítása. Ha primer percutan coronariaintervenció elérhető, akkor ez a választandó kezelési stratégia ST-szegment-elevációval járó myocardialis infarctusban. Cél: Jelen cikkben a Szombathely városból ST-szegment-elevációval járó akut szívinfarktussal kórházba került betegek 3 hónapos halálozását vizsgáltuk. Módszer: Két időszakot hasonlítottunk össze, 2005-öt, amikor nem volt helyben percutan coronariaintervencióra alkalmas szívkatéteres laboratórium és 2008-at, amikor helyben rendelkezésre állt a primer percutan coronariaintervenció. Eredmények: A 12 órás ischaemiás időszaknál rövidebb betegcsoportban a 3 hónapos halálozás 2008-ban lényegesen alacsonyabb volt a 2005-ös évhez képest (3,6% versus 15,6%). Elsősorban a fibrinolízissel kezelt betegcsoport magas, három hónapos mortalitása volt felelős a különbségért. Ugyancsak fontos, hogy 2008-ban csökkent a 12 órán túli betegek aránya 2005-höz képest. Következtetés: A szívkatéteres labor létrehozása kedvező hatással volt Szombathely város ST-elevációs infarktusos betegeinek kórlefolyására. | Treatment of acute myocardial infarction has changed in recent years. Tremendous debate has developed over the efficacy of percutaneous coronary intervention compared with fibrinolysis. If primary percutaneous coronary intervention is available, it is the preferred treatment for acute ST segment elevation myocardial infarction. Aim: Three months mortality of patients admitted to hospital with ST elevation myocardial infarction in city of Szombathely was analyzed. Methods: Mortality rates of two time periods were compared: year 2005 without primary percutaneous coronary intervention capability and year 2008 when local primary percutaneous coronary intervention was available. Results: In patient group with no longer than 12 hours ischaemic period 3 months mortality rate was lower in 2008 compared to 2005 (3.6 % versus 15.6 %). First of all, the relative high 3 months mortality rate in patient group treated with fibrinolytic therapy was responsible for this difference. Decreasing number of patients with longer than 12 hours ischaemic time in 2008 versus 2005 was also important. Conclusion: Implementation of primary percutaneous coronary intervention for the management of ST segment elevation myocardial infarction patients in Szombathely was effective for patients’ outcome