Field sensing using the magnetoresistance of IrMn exchange-biased tunnel junctions

An original concept of high sensitivity magnetic field sensor using the spin-dependent tunneling effect has been investigated. The required crossed-biased configuration is obtained by combining both shape energy originating from vicinal step bunched Si substrates and unidirectional exchange anisotropy supplied by an Ir ₂₀Mn ₈₀ film in the "top-biased" geometry. We demonstrate a linear and reversible signal at room temperature and above. The smooth loss of sensitivity at higher temperature is shown to be correlated to the thermal dependence of the exchange bias property when IrMn is deposited above the insulating Al ₂O ₃ barrier.