Thermomagnetically controlled setting of double-biased hysteresis in NiFe/IrMn films with a single ferro-antiferromagnet interface

Abstract

Exchange bias of NiFe/IrMn and NiFe/Cu/IrMn structures was modulated by thermal exposures in a magnetic field. The temperature ramping cycles consisted of three phases: Heating from room temperature (RT) 22 °C to exposure temperature TEXP (heating phase), exposure at TEXP with applied field HEXP (settled phase), and cooling from TEXP down to 22 °C (cooling phase). Contributions of these phases into resulting exchange bias in the exposed sample are distinguished. Dynamic exposure with the field applied during heating and cooling leads to a gradual shift of the RT M(H) loop from negative to positive fields. Static exposure with the field on when the temperature is settled only leads to the formation of a complex transitional hysteresis with two sub-loops. The magnetization at the intermediate state of this hysteresis depends on TEXP with a threshold indicating percolation magnetization reversal in the network of the interfacial grains. The revealed mechanisms of the thermal exposure effects could be helpful in the development of technological processes for definition of magnetic anisotropies in multilayer sensors and memory structures with accurate control of magnetization angles.