鎳鐵/鈷鐵/氧化鋁/鈷鐵/鈮 鄰近效應影響下的穿隧磁電阻率

Abstract

摘要 磁性穿隧接面由鐵磁/絕緣/鐵磁所構成，穿隧磁電阻效應的高低主要取決於「鐵磁/絕緣」介面上的磁性和電子組態。藉由引入超導層，在鐵磁/超導鄰近效應中，我們來觀察鐵磁層中電子傳輸是否受到超導層影響。經由對照組我們發現在低溫進入超導態時，反平行態電阻受到超導層鈮的影響隨著溫度降低而降低，而平行態電阻則不受超導影響，其現象就是磁電阻率的降低。

在不同厚度的鈮，我們發現鈮厚度在低於100 nm時，磁電阻率在超導態時明顯不受影響。比較鈮厚度500 nm，鈮厚度在150 nm ~250 nm時，磁電阻率在溫度降低至超導轉變溫度時會有延遲降低的現象。

Abstract

The magnetic tunnel junctions (MTJs) are consisted of ferromagnet/insulator/ferromagnet (FM/I/FM). Tunnel magnetoresistance (TMR) is strongly influenced by the electronic and magnetic properties at the FM/I interface. Considering the proximity effect in ferromagnet/superconductor (FM/SC), we sputtered Nb on the top FM layer of pseudo spin-valve (PSV) magnetic tunnel junctions to observe how the superconducting Nb influences the FM layer. With the help of the contrast experiment, we find that the resistance of the antiparallel state maybe influenced by Nb and it becomes lower below the superconducting transition temperature (Tc). However, the resistance in paralleled state is not significantly influenced by Nb, resulting in the decrease of TMR values. In the thickness dependence of Nb, we find that TMR is not apparently influenced in SC state as the thickness of Nb is below 100 nm. Comparing with that in the case of 500 nm Nb thickness, the TMR value shows retarding decrease as cooling through Tc for those of Nb thickness between 150 nm and 250 nm.