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Field detection in single and double barrier MgO magnetic tunnel junction sensors

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3 Author(s)
Almeida, J.M. ; Instituto de Engenharia de Sistemas e Computadores-Microsistemas e Nanotecnologias (INESC-MN), Lisbon, Portugal and Instituto Superior Técnico, Physics Department (IST), Lisbon, Portugal ; Wisniowski, P. ; Freitas, P.P.

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Single and double barrier MgO based magnetic tunnel junction sensors were processed with area of 200 μm2 and small aspect ratios (≪2). These sensors present resistance area products ranging from 10 to 70 kΩ μm2 and tunneling magnetoresistance (TMR) values of up to 160%. Sensor linearization was mostly obtained by thinning the CoFeB free layer to 15.5 A, close to the free layer transition from ferromagnetic to superparamagnetic behavior. Three different thicknesses were studied for the free layer CoFeB: 1.55, 1.8, and 3 nm. The CoFeB thickness decrease required for the linearization implies a loss in TMR. Field detection range of ∼80 pT/Hz0.5 was obtained for both double and single barrier sensors (at 500 KHz). Out of the 1/f regime, the detection range decreases to ∼2 pT/Hz0.5 for the single barrier sensor. The field detection dependence on bias voltage was also studied at 500 KHz and outside the 1/f dominated regime.

Published in:

Journal of Applied Physics  (Volume:103 ,  Issue: 7 )