- 學位論文
C軸取向六方結構鎦鐵氧薄膜之製備與磁電特性分析
Preparation and Magnetoelectric Properties of the C-axis-oriented Hexagonal LuFeO3 Thin Film
摘要
近年來，同時具有鐵電極化和磁有序排列的多鐵材料開始被廣泛研究，其中包含被預期具有室溫多鐵性的h- LuFeO3。本研究成功藉由脈衝雷射沉積系統(PLD)將h- LuFeO3薄膜成長於YSZ(111)基板上，且無任何雜相，薄膜表面也非常平坦。在127 K時發現h- LuFeO3具有反鐵磁之相變；在73 K時發現有磁矩重新排列的現象，此為先前文獻中未被報導之相變溫度，僅於單晶中出現。有趣的是，由於Dzyaloshinskii－Moriya 作用的貢獻，h- LuFeO3在c軸具有微弱的鐵磁行為，在10 K時矯頑磁力400 Oe，甚至於在300 K時仍有100 Oe，提升此多鐵材料在元件應用上的潛力。除此之外，發現了h- LuFeO3在400 K時仍有鐵電特性，且在低溫時也發現磁電耦合的現象。
並列摘要
Recently, the multiferroic materials with the coexisting ferroelectric polarization and magnetic order have been extensively studied, including h-LuFeO3 which is expected to have room-temperature multiferroicity. In this study, the h-LuFeO3 thin films have been successfully grown on a YSZ (111) substrate by a pulsed laser deposition system (PLD) without any impurity phase Moreover, the film surface is very flat. Experimental results reveal that there are an antiferromagnetic phase transition and a spin reorientation transition occurring at 127 K and 73 K, respectively, in the present h-LuFeO3 films. It is noted that the latter transition has not been reported in previous thin film studies, but appeared only in single crystals. Interestingly, due to the contribution of Dzyaloshinskii-Moriya interaction, h-LuFeO3 also exhibits a weak ferromagnetism along the c-axis with a coercivity field of 400 Oe at 10 K, and 100 Oe at 300 K, respectively. This unique feature may further enhance the potential applications of this multiferroic material. In addition, it is found that the ferroelectricity of h-LuFeO3 can sustain up to 400 K, whereas the magnetoelectric coupling can only be observed at low temperatures.