利用PZT之形變控制鎳薄膜磁彈性異向能
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2017
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本論文主要是利用壓電材料PZT通電壓後造成的形變，進而扯動黏在上層的磁性薄膜，藉由此機制觀察磁性薄膜的磁性行為。壓電材料PZT加上磁性薄膜的組合稱為人工多鐵性(Artificial Multiferroic)，即自組裝鐵磁性材料和鐵電性材料，因為要在一塊材料中同時存在鐵磁性和鐵電性並不容易達成，所以我們可以藉由此方法得到想要的結果。
我們發現將Pd/Ni/Pd三層膜鍍在雲母片上，再將此樣品黏於2 mm厚的PZT，通入電壓後可以得到有序且有趣的磁性變化，我們也發現對電場和矯頑力(Coercivity)作圖，在小場附近(0 V/mm到15 V/mm附近)會有不連續的現象，且最後回到0 V/mm時和原來的Coercivity會不一致，從文獻中得知鎳薄膜的磁矩從水平異向性翻轉到垂直異向性所需要的能量為0.16 MJm^-3。同時我們也使用應變計(Strain Gauge)測量PZT的形變，以及PZT傳遞到雲母片上的應力，分別是0.507‰及0.465‰，由此我們可以得知整塊PZT形變與電場的關係，且PZT在被極化後的形狀和未極化前不一樣，但遵守體積守恆定律。
利用X光繞射分析儀(X-Ray Diffraction)分析薄膜的晶格結構，再和幾篇文獻對照，得知我們所使用的鋯鈦酸鉛為PZT(111)，成長的薄膜為Pd(111)和Ni(111)，另外，我們也鍍了鐵和鈷兩種不同的磁性薄膜在壓電銅片-蜂鳴器上，做了一系列有趣的量測，雖然並沒有發現磁性行為的改變，但我們對其形變有初步的了解。
關鍵字：鋯鈦酸鉛PZT、磁致伸縮、磁電效應
Multiferroics has attracted much attention in the last decade due to its potential of application. However, the intrinsic coupling between multiferroic phases in single material is hard to achieved at room temperature. Alternatively, in this study, we chose an "artificial" multiferroic material called magnetoelectric (ME) composite to investigate the voltage-assisted ME coupling by combining piezoelectric Pb(Zr,Ti)O3 (PZT) material and magnetostrictive Ni layers. When a voltage applied on PZT, the ME response results from the electric field-induced strain transferring from PZT to Ni and cause the change of magnetism. The magnetic coercivity Hc of the sample Pd/Ni/Pd/Mica/PZT(2 mm) with respect to applied electric field is non-linear in the range between 0 and 15 V/mm. However, we obtained some regular changes of the magnetic behavior in high voltage range. When the voltage turned off to 0 V, Hc is not recovered to the initial value. We determine the strain of PZT and mica are 0.507‰ and 0.465‰ by strain gauge, respectively. X-ray diffractometer (XRD) pattern shows that crystal planes of PZT, Pd and Ni are in [111] direction. Furthermore, we also studied the ME effect in (Fe, Co)/Buzzer system, the Hc doesn't change by certain deformation of buzzer. Key words：Lead zirconate titanate, PZT, Magnetostriction, Magnetoelectric Effect
Multiferroics has attracted much attention in the last decade due to its potential of application. However, the intrinsic coupling between multiferroic phases in single material is hard to achieved at room temperature. Alternatively, in this study, we chose an "artificial" multiferroic material called magnetoelectric (ME) composite to investigate the voltage-assisted ME coupling by combining piezoelectric Pb(Zr,Ti)O3 (PZT) material and magnetostrictive Ni layers. When a voltage applied on PZT, the ME response results from the electric field-induced strain transferring from PZT to Ni and cause the change of magnetism. The magnetic coercivity Hc of the sample Pd/Ni/Pd/Mica/PZT(2 mm) with respect to applied electric field is non-linear in the range between 0 and 15 V/mm. However, we obtained some regular changes of the magnetic behavior in high voltage range. When the voltage turned off to 0 V, Hc is not recovered to the initial value. We determine the strain of PZT and mica are 0.507‰ and 0.465‰ by strain gauge, respectively. X-ray diffractometer (XRD) pattern shows that crystal planes of PZT, Pd and Ni are in [111] direction. Furthermore, we also studied the ME effect in (Fe, Co)/Buzzer system, the Hc doesn't change by certain deformation of buzzer. Key words：Lead zirconate titanate, PZT, Magnetostriction, Magnetoelectric Effect
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鋯鈦酸鉛PZT, 磁致伸縮, 磁電效應, Lead zirconate titanate, PZT, Magnetostriction, Magnetoelectric Effect