Magnetska svojstva multiferoika BiFeO3 dopiranog gadolinijom

master's thesis

• Title (english): Magnetic properties of multiferroic BiFeO3 doped with gadolinium
• Author: Jure Dragović
• Mentor: Damir Pajić (mentor)
• Committee member: Damir Pajić (predsjednik povjerenstva)
• Committee member: Emil Tafra (član povjerenstva)
• Committee member: Vito Despoja (član povjerenstva)
• Committee member: Krešo Zadro (član povjerenstva)
• Committee member: Danko Radić (član povjerenstva)
• Granter: University of Zagreb; Faculty of Science; (Department of Physics); Zagreb
• Defense date and country: 2015-06-19, Croatia
• Scientific / art field, discipline and subdiscipline: NATURAL SCIENCES; Physics

Abstract

Multiferoici su multifunkcionalni materijali koji pokazuju istovremeno više parametara uređenja. Međusobna povezanost tih uređenja, pogotovo feroelektričnog i magnetskog otvara mogućnost tehnološke upotrebe. U ovom radu istraživana su magnetska svojstva perovskitnog multiferoika BiFeO3 dopiranog s različitim postotcima gadolinija pomoću MPMS SQUID magnetometra. Osim uobičajenih niskotemperaturnih magnetskih svojstava pomoću posebnog dodatka za MPMS SQUID magnetometar izmjerena su... More visokotemperaturna svojstva uzoraka, u intervalu od 2 do 800 K. Opažen je fazni prijelaz na 640 K koji opada do 635 K sa povećanjem koncentracije gadolinija te veliko razdvajanje ZFC i FC krivulja koje potječe od slabog feromagnetskog uređenja. Magnetske histereze su mjerene do polja od 5 T gdje nije bilo znakova saturacije. BiFeO3 ima antiferomagnetske histereze sa malim koercitivnim poljima koje opada sa porastom temperature, dok dopirani uzorci pokazuju veliko koercitivno polje koje u određenom temperaturnom intervalu neuobičajeno raste sa porastom temperature. Mjerenja u električnom polju su pokazala male promjene u iznosu magnetizacije, ali ne i promjene u ponašanjima magnetizacije, ukazujući na čvrstu magnetsku strukturu. BiFeO3 dopiran gadolinijem ima veći magnetski moment od antiferomagnetskog, čistog, BiFeO3, ali dopiranjem nije postignuto primjetljivo magnetoelektrično vezanje. Iako je BiFeO3 jedan od rijetkih multiferoika na sobnoj temperaturi, njegova tehnološka upotreba je stoga ograničena zbog malog magnetoelektričnog efekta, čak i u slučaju izazvanog slabog feromagnetizma prilikom provedenog dopiranja. Less

Abstract (english)

Multiferroics are multifunctional materials that exhibit multiple ferroic orders at the same time. Combination of ferroelectric and magnetic order opens possibilities for technological applications. Magnetic properties of perovskite multiferroic BiFeO3 doped with different concentrations of gadolinium were investigated with MPMS SQUID magnetometer. Apart from usual low temperature magnetic properties, using the special inset for MPMS SQUID magnetometar, high temperature... More properties of all the samples were measured in temperature interval of 2 to 800 K. Phase transition was observed at 640 K, which decreases with increase of gadolinium concentration down to 635 K, as well as huge separation between ZFC and FC curves, as a result of increasing concentration of gadolinium ions, was observed. Magnetic hysteresis loops were measured up to 5 T and no signs of saturation were visible. BiFeO3 exhibits characteristic antiferromagnetic hysteresis curves with small coercive field which decreases with temperature, while the doped samples exhibit large coercive field which increases in particular temperature interval. Magnetization measured in electric field showed small changes in magnetic moment, but significant change in magnetization behaviour was absent which indicates strong magnetic structure of BiFeO3. Although BiFeO3 doped with gadolinium exhibits higher magnetic moment than the pure phase of BiFeO3, it doesn’t lead to noticeable magnetoelectric coupling. BiFeO3 is one of the rare room temperature multiferroics but it’s low magnetoelectric coupling limits it’s technological perspective, even in the case of induced weak ferromagnetism after performed doping. Less

• Keywords: multiferoik; magnetska svojstva perovskitnog multiferoika BiFeO3
• Language: croatian
• URN:NBN: urn:nbn:hr:217:786697
• Study programme: Title: Physics; specializations in: Research; Course: Research; Study programme type: university; Study level: integrated undergraduate and graduate; Academic / professional title: magistar/magistra fizike (magistar/magistra fizike)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Open access
• Created on: 2017-04-04 20:08:06