Evolution of structural and magnetic properties of NiFe/NiO exchange biased bilayer with medium energy C plus ion irradiation

Exchange bias systems have attracted much attention in high-efficiency spintronic magnetic memory devices. Still, heavy ion irradiation can change the microstructure and magnetic properties and then affect the stability of the device in extreme environments. This work systematically reports the structural and magnetic behavior of NiFe/NiO bilayer films under different irradiation doses of 1.08 MeV medium-energy C+ ions. With the increase of irradiation doses, the intensity of NiO (111) diffraction peak decreases and the grain size reduces from 30.6 nm to 24.4 nm. At the lower 1 x 1014 ions/cm2 dose, the exchange bias field obtained by static and dynamic magnetic measurements shows the lowest value. This occurs because of an instability defect that disrupts the order of the FM-AFM interface. However, at a higher dose (>= 5 x1014 ions/cm2), defects at the interface form a new pinning center, enhancing the exchange bias field. The thermal stability of the device is less affected by this high dose of C+ ion irradiation. Compared to other low-energy or high-energy ions, this system can withstand a wider range of irradiation doses from medium-energy C+ ions. It is of great significance to further understand the influence of different irradiated energies and doses on the properties of magnetic film and design magnetic memory devices.