Detection of Sub-Nano-Tesla Magnetic Field by Integrated Magnetic Tunnel Junctions with Bottom Synthetic Antiferro-Coupled Free Layer

作者：Fujiwara Kosuke^*; Oogane Mikihiko; Nishikawa Takuo; Naganuma Hiroshi; Ando Yasuo

来源：Japanese Journal of Applied Physics, 2013, 52(4).

DOI：10.7567/JJAP.52.04CM07

Arrays of 100 x 100 magnetic tunnel junctions (MTJs) connected in parallel and series were fabricated. A synthetic antiferro-coupled bottom free layer with a NiFe/Ru/CoFeB structure and MgO tunneling barrier were used to realize a high sensitivity, which is defined as TMR/2H(k), where, TMR is the tunneling magnetoresistance ratio and H-k is the magnetic anisotropy field of the free layer. To obtain a linear response of tunneling resistance against an applied external magnetic field, a double annealing process was carried out. From R-H curve measurements, the sensitivity of the 100 x 100 integrated MTJs was lower (8%/Oe) than that of a single MTJ (25%/Oe). However, a 1/30 decrease in noise power density was realized in the integrated MTJs. Consequently, a very small magnetic field of 0.29 nT was detected with the integrated MTJs.

• 出版日期2013-4