پديد آورنده :
حكيمي، محسن
عنوان :
ساخت و مطالعه ي ويژگي هاي ساختاري و مغناطيسي برخي از آلياژهاي هويسلر
محل تحصيل :
اصفهان: دانشگاه صنعتي اصفهان، دانشكده فيزيك
صفحه شمار :
نه،132ص.: مصور،جدول،نمودار
يادداشت :
ص.ع.به فارسي و انگليسي
استاد راهنما :
پرويز كاملي
استاد مشاور :
هادي سلامتي
توصيفگر ها :
مدل اسليتر , پائولينگ
تاريخ نمايه سازي :
5/12/91
استاد داور :
مجتبي اعلايي، محمد الماسي، مرتضي مظفري
كد ايرانداك :
ID502 دكتري
چكيده فارسي :
به فارسي و انگليسي: قابل رويت در نسخه ديجيتالي
چكيده انگليسي :
Abstract In this project Co2Fe1 xCrXAl Heusler alloys have been prepared by mechanical alloying MA Final Fm3m phase was obtained after 15 hours of milling The analysis of X ray data confirms the existence of the CoAl phase in the samples obtained after one hour of MA With the increased Fe content the reduction in peak intensity over time is not as rapid This phenomenon can be related to the catalytic effects of Cr for all of the samples Ms is less than the estimated Slater Pauling value The deviation of the magnetic moment per formula unit from the theoretical Slater Pauling value decreases with the increasing Fe content which is attributed to a very low moment at the Cr sites Also the effect of annealing and mechanical properties of these compounds was studied Then four Heusler compounds Co2FeGe Co2FeSi Fe2CoGe Fe2CoSi were prepared with the same method and effect of vacuum annealing on properties was studied According to the structural measurements 15 hours milling was enough for crystallization of these compounds During annealing the crystallite size increased and lattice ordering enhanced Two super lattice peaks was appeared in X ray spectrum due to enhancement of lattice ordering of two Si content compounds In Co based compounds the saturation magnetization value increased to a closer value of Slater Pauling model because of improvement of lattice ordering The value of Ms in some Fe based compounds was higher than Slater Pauling prediction The magnetic structure of these samples was analyzed by mosbauer spectroscopy and the atomic moments were determined At the end 6 compounds of 24 valence electron Heusler alloys were prepared Investigation of properties of ball milled Mn3 xGa samples showed that the stoichiometry of these compounds will change during milling process so all of these 24 valence electron samples were prepared by arc melting Fe2TiGe and Fe2TiSi were no single phase 5 samples of Mn3Ga were prepared The difference between these samples was the annealing temperature and the ball milling process after arc melting The ball milled and annealed samples had L10 and DO22 structures respectively The saturation magnetization deviated from Slater Pauling value in annealed samples The annealed samples showed a coercive field in range of 0 7T The X ray measurements showed that a little Mn is exsolved at the two higher annealing temperatures One of these samples had a 4 times higher magnetization and same coercivety in comparison with previous works Cr 2CoGa sample had L21 structure but magnetization deviated from Slater Pauling value In contrast Cr2FeGe had a tetragonal structure The magnetic structure of this sample was studied by mosbauer spectroscopy measured at 20 and 300K and a change in magnetic structure was detected by temperature Magnetization of Fe2VGa was too low This value was explained with a weak itinerant ferromagnet state
استاد راهنما :
پرويز كاملي
استاد مشاور :
هادي سلامتي
استاد داور :
مجتبي اعلايي، محمد الماسي، مرتضي مظفري
