Low frequency noise in asymmetric double barrier magnetic tunnel junctions with a top thin MgO layer

• Published in: Chinese physics B Vol. 24; no. 7; pp. 78504 - 1-078504-4
• 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: 01.07.2015
• Subjects: Antiferromagnetism; Asymmetry; Barriers; Ferromagnetism; Low frequencies; Magnesium oxide; Magnetoresistance; Noise
• ISSN: 1674-1056; 1741-4199
• 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 alpha sub(mag). 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 alpha sub(mag) and magnetoresistance-sensitivity-product show a linear dependence, consistent with the fluctuation dissipation relation. With the magnetic field applied at different angles ([straighttheta]) to the easy axis of the free layer, the linear dependence persists while the intercept of the linear fit satisfies a cos([straighttheta]) dependence, similar to that for the magnetoresistance, suggesting intrinsic relation between magnetic losses and magnetoresistance.