Measurement And Magnetoelectric Coupling Of Exchange Bias Field Of NiFe/FeMn Multilayers

With the rapid development of modern industry,the development of electronic devices tends to be miniaturized and high frequency,and the demand for high frequency magnetic films is also increasing.The exchange bias effect is widely studied as an important means to control high frequency magnetic properties.However,because the exchange bias effect is a complex interface effect,many fundamental aspects of the EB mechanism are still not well established.In this paper,we investigate the different methods for measuring the exchange bias field and magnetoelectric coupling effects of exchange bias multilayers.A series of NiFe(15 nm)/FeMn(t AF)exchange-biased bilayers were fabricated by magnetron sputtering,three different methods were used to measure the exchange bias field of the thin films.The first One was traditional vibrating sample magnetometer(VSM),the second one was the anisotropic magnetoresistance(AMR)technique,the last one was vector network analyzer ferromagnetic resonance(VNA-FMR)technique.The results show that,for the sample at the critical thickness,the exchange bias field obtained by AMR and VNA-FMR were much larger than that of VSM,which can be explained by the unstable coupled grains at the interface.For the sample at the saturation thickness,the measurement values of the three methods are almost the same.Through the preparation of PMN-PT/Ta/ [Ni Fe/Fe Mn]N/Ta multiferroic heterostructure,the magnetoelectric coupling effect of the exchange bias multilayers was studied.We found that the static magnetic changes of the multilayer films were similar after the application of the electric field,but in the dynamic magnetic field,the resonance frequency of the ferromagnetic layer pinned by a single Fe Mn layer at the bottom layer changed little.The resonant frequency of the middle ferromagnetic layer was pinned by two Fe Mn layers changes to about 1 GHz.The above results were all tested by removing the electric field after the electric field was applied,and the non-volatile modulation of the magnetic field by the electric field was realized.