Low frequency noise in asymmetric double barrier magnetic tunnel junctions with a top thin MgO layer Project supported by the National Basic Research Program of China (Grant Nos. 2011CBA00106, 2012CB927400, 2010CB934401, and 2014AA032904), the National High Technology Research and Development Program of China (Grant No. 2014AA032904), and the National Natural Science Foundation of China (Grant Nos. 11434014 and 11104252)

• Published in: Chinese physics B Vol. 24; no. 7
• Main Authors: Guo, Hui-Qiang, Tang, Wei-Yue, Liu, Liang, Wei, Jian, Li, Da-Lai, Feng, Jia-Feng, Han, Xiu-Feng
• Format: Journal Article
• Language: English
• Published: IOP Publishing 29.05.2015
• Subjects: 1/f noise; double barrier magnetic tunnel junctions; fluctuation dissipation relation; magnetic tunnel junctions
• ISSN: 1674-1056
• DOI: 10.1088/1674-1056/24/7/078504

Low frequency noise has been investigated at room temperature for asymmetric double barrier magnetic tunnel junctions (DBMTJs), where the coupling between the top and middle CoFeB layers is antiferromagnetic with a 0.8-nm thin top MgO barrier of the CoFeB/MgO/CoFe/CoFeB/MgO/CoFeB DBMTJ. At enough large bias, 1/f noise dominates the voltage noise power spectra in the low frequency region, and is conventionally characterized by the Hooge parameter αmag. With increasing external field, the top and bottom ferromagnetic layers are aligned by the field, and then the middle free layer rotates from antiparallel state (antiferromagnetic coupling between top and middle ferromagnetic layers) to parallel state. In this rotation process αmag and magnetoresistance-sensitivity-product show a linear dependence, consistent with the fluctuation dissipation relation. With the magnetic field applied at different angles (θ) to the easy axis of the free layer, the linear dependence persists while the intercept of the linear fit satisfies a cos(θ) dependence, similar to that for the magnetoresistance, suggesting intrinsic relation between magnetic losses and magnetoresistance.