Multiréteg struktúrák mágneses tulajdonságai = Magnetic properties of multilayer structures

A nanometeres skalaju szerkezet, a hatarfeluleti keveredes es a magneses tulajdonsagok kapcsolatat tanulmanyoztuk Fe-Al es Fe-Ag multiretegekben es nano-kompozitokban. Az ultravekony retegvastagsagu Fe-Al multiretegekben tapasztalt szokatlanul nagy magneses anizotropiat a ket monoreteg vastagsagu Fe tartomanyoknak tulajdonitottuk, miutan ezek megjeleneset az alacsony hőmersekleten mert Fe hiperfinom terek alapjan kimutattuk. A szuperparamagneses tulajdonsagok alapjan meghataroztuk a nem-folytonos Fe retegű Fe-Ag multiretegekben talalhato Fe szemcsek meretet. A tombi magnesseg meresek es a lokalis jellegű Mossbauer spektroszkopia hasonlo eredmenyeket adott es ezekből arra kovetkeztettunk, hogy a Fe szemcsemerete csokken az Ag elvalaszto reteg vastagsaganak novekedesevel. Bizonyos szemcsemeret alatt egy kozel merőleges magneses anizotropiat tapasztaltunk, amiről megmutattuk, hogy fuggetlen az olyan mechanikai feszultsegektől, amely a hőtagulasbol vagy fedőreteg alkalmazasabol szarmazik. A komponensek egyuttes parologtatasaval keszitett Fe-Ag granularis otvozetek eseten azt talaltuk, hogy a Fe szemcsek merete ugyancsak a nanometeres tartomanyba esik, de merőleges magneses anizotropiat nem tapasztaltunk. Tobb mint ket komponensű multiretegek eseten bevezettuk a szekvencia permutalt multiretegek gondolatat es alkalmaztuk arra, hogy a Fe reteg felső (Fe/B) es also (B/Fe) hatarreteget vizsgaljuk Ag/Fe/B es Ag/B/Fe szekvencia permutalt multireteg parokban. | The connection between the nanoscale structure, the interface mixing and the magnetic properties were studied in Fe-Al and Fe-Ag multilayers and nanoscale composites. The unusually large magnetic anisotropy of ultrathin Fe-Al multilayers has been related to two monolayer thick Fe regions deduced from the low temperature Fe hyperfine fields. The size of Fe grains in Fe-Ag multilayers with discontinuous Fe layers could be determined from the superparamagnetic properties. Bulk magnetization and local Mossbauer spectroscopy measurements gave similar results and the decrease of the grain size with increasing Ag spacer thickness was deduced. Below certain grain-size a close to perpendicular magnetic anisotropy was observed, which was shown to be independent of mechanical stresses arising from heat dilatation or application of cover layer. Fe-Ag granular alloys prepared by co-evaporation of the components were found to contain Fe grains also in the nano-size range, but no perpendicular magnetic anisotropy could be observed. The notion of sequence permutated multilayers with more than two components was introduced and applied to investigate the top (Fe/B) and bottom (B/Fe) interfaces of Fe with B in Ag/Fe/B- and Ag/B/Fe sequence permutated multilayer pairs. The results show that both interfaces are amorphous, but B concentration of the top interface is higher.