正交結構鐿錳氧(100)薄膜之磁電特性研究

Abstract

本實驗室成功的使用脈衝雷射濺鍍系統在鍶鈦氧(110)基板成長 出類單晶之正交結構的(100)軸向鐿錳氧薄膜，並對此一具E-type 反 鐵磁結構之稀土族錳氧化物的磁電特性作更進一步的探討。使用超導 量子干涉儀量測鐿錳氧薄膜在不同軸向的磁化特性，發現在b 軸方向 低於反鐵磁尼爾溫度(~43K)以下還有另外一個磁相變存在。我們更進 一步使用LCR Meter 量測薄膜之介電常數與溫度之變化關係，並與前 述磁化特性比較結果顯示正交結構鐿錳氧薄膜在35.8K 左右存在一 個反鐵磁態不相稱-相稱的相轉變。惟在a 軸方向進行電極化向量與 電場關係的量測時，吾人並未發現如理論預測的磁相變誘發鐵電極化 顯著效應。

We have successfully obtained the a-axis-oriented orthorhombic YbMnO3 (100) thin films grown on SrTiO3(110) substrate by pulsed laser deposition (PLD).The nearly-single-crystalline characteristic of these films allow us to probe the electric and magnetic properties of the rare-earth manganites with E-phase antiferromagnetic(AFM) structure. We measured the susceptibility of YbMnO3 thin film along different crystalline axes by SQUID (Superconductor Quantum iii Interference Device), and observed that these in another phase transition at temperatures below the AFM Néel Temperature TN. The temperature dependent dielectric constant ε of the films was measured by LCR Meter, and was compared with the magnetization results. The results indicate that the orthorhombic YbMnO3 does have an extra commensurate to incommensurate phase transition within the AFM state at 35.8 K. The direct polarization measurements along the a-axis, however, did not reveal the significant magnetism-induced ferroelectricity as anticipated by the theoretical prediction.