Pseudo spin-valves with different spacer thickness as sensing elements of mechanical strain

摘要

Giant magnetoresistance (GMR) effect in cobalt based pseudo spin-valves (SV) is combined with the inverse magnetostriction in sensors of mechanical strain. SV with Co/Au/Co core structure were deposited onto the flexible 125 μm thick polyimide substrates. The influence of magnetostriction on GMR was studied in bending current-in-plane configuration. Total relative strain was between -8.6 × 10 ~(-3) (compression) and 8.6 × 10 ~(-3) (tension). SV were designed with respect to the oscillating nature of exchange coupling force vs. spacer thickness. The period of oscillations is not changing under the applied stress in our experimental configuration. From the magnetoresistance ratio vs. strain dependences it follows that the output signal of the strained sensor vs. unloaded one could be improved by a proper choice of the spacer thickness t _s. If t _s = 4 nm the relative output is 36% and for t _s = 2.4 nm it is 34%, however, in this case only in the half range of the strain between 0 and ±8.6 × 10 ~(-3). For t _s = 2.2 nm the relative output is only 10%.