Change in blocking temperature of nanoparticle array deposited on magnetoresistive sensor

Here we present the effect of ferromagnetic magnetoresistive sensor on magnetic susceptibility of nanoparticles (NPs) deposited on its surface. Deposition of the CoFe ₂O ₄ nanoparticles on the CoFeB/Ta/CoFeB platform, comprising thin ferromagnetic layers, changes the blocking temperature of the NPs. The magnetic dipole interaction between the NPs and the platform affects the frequency and field dependences of the blocking temperature of the NPs, because the effective energy barrier of magnetization reversal is higher than in NPs deposited on a diamagnetic substrate. Obtained results demonstrate backward effect of the sensor on the analyzing NPs array. An allowance of this effect is important for the correct application of a magnetoresistive and low frequency inductive sensors in medicine and biology.