Effect of α-Fe2O3 microbeads on CoFeB/Ta/CoFeB magnetic switching and magnetic instabilities

Effect of cell microbeads labelled with commercial α-Fe2O3 nanoparticles (NPs) on magnetic properties of MgO/CoFeB/Ta/CoFeB/MgO/GaAs spin valves and monolayer system MgO/CoFeB/MgO/GaAs was observed. Magnetic scattering field of α-Fe2O3 microbeads shifts critical magnetic field (CMF) of magnetization switching of free layer in spin valves. The CMF is controlled by energy balance of magnetic anisotropy, interlayer exchange coupling, Zeeman energy and scattering magnetic field of microbeads. Local magnetic field of microbeads and their effect on CMF were estimated accordingly with the magnetic profile of the surface scanned by magnetic force microscope. Magnetic instability of film magnetization caused by magnetic microbeads deposited on the spin valve surface was revealed.