C軸取向正交結構鎦鐵氧薄膜之磁性與電特性分析

Abstract

正交結構(orthorhombic)的LuFeO3為一種新的磁電耦合多鐵材料。此材料在a軸和b軸具有反鐵磁性，其中a軸磁矩在c軸又有傾斜，造成LuFeO3在c軸有微弱的鐵磁性。在電性方面，LuFeO3室溫下在c軸有鐵電性。然而，近幾年來的研究以粉末為主，成長正交結構之LuFeO3薄膜文獻是非常缺乏的。由於LuFeO3的磁電特性具有強烈的各向異性(anisotropy)，因此成長LuFeO3軸向明確的薄膜，是一個非常有潛力且有助於發展和應用的研究方向。本論文首先利用高溫燒結法製作LuFeO3之靶材，再以脈衝雷射沉積法(PLD)將LuFeO3薄膜成長於NSTO(100)基板上，再以X光繞射儀、原子力顯微鏡、超導量子干涉儀和LCR meter分別量測薄膜結構、粒徑大小、磁性和電性，分析比較其性質。

Orthorhombic ferrites (o-RFeO3, R=Sm,Dy,Lu) are known to be ferroelectric because of the polar structure, which is of the same origin of the ferroelectricity exhibited in SmFeO3. Moreover, a weak ferromagnetic ordering induced ferroelectric polarization has been found in LuFeO3 recently. However, the research of LuFeO3 in the thin film form is lacking, which is desirable to in order to harvest the magnetically induced polarization anticipated for application. In this thesis, we will present the preparation and properties of orthorhombic rare earth multiferroic LuFeO3 thin films. Briefly, sintered ceramic pellet of LuFeO3 was prepared by solid-state reaction and used as the target for the subsequent pulsed laser deposition. LuFeO3 thin films grown on various substrates were characterized by x-ray diffraction (XRD), atomic force microscope (AFM). Moreover, the temperature dependences magnetization (M-T) measurements, dielectric constant (r’-T), dielectric loss (tanδ-T), and conductivity (σa.c.-T) will be presented and discussed.