Large Area and Low Aspect Ratio Linear Magnetic Tunnel Junctions With a Soft-Pinned Sensing Layer

Large area MTJs with linear response and very larger sensitivities are needed to fulfill the requirements for the detection of pT/Hz<sup>0.5</sup> magnetic fields at low frequency and room temperature. MTJ stacks with soft-pinned sensing layers have been developed and the stack was optimized, providing a tunable soft-pinning field over a large range of values. Sensitivities corresponding to resistance changes of up to 7%/Oe are obtained in patterned MTJs with areas of 20 × 20 μm<sup>2</sup> starting from films with high sensitivity soft-pinned layers made from 3.0Co<sub>40</sub>Fe<sub>40</sub>B<sub>20</sub>/0.21Ta/8.0Ni<sub>81</sub>Fe<sub>19</sub>/8.0Ir<sub>20</sub>Mn<sub>80</sub>.

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