Epitaxial Growth Of The FeGa/PMN-PT Film And Electric Control Of Magnetism Study

Non-volatile,high reading and writing speed,high storage density,low power consumption and device miniaturization are the main trends of magnetic memory in the future.Energy consumption increases significantly for the process of magnetic information writing,mainly because the current density must be greater than the critical current density to reach the target.In contrast,electric control of magnetism not only significantly reduces the effect of joule heat,but also enables low-power,high-density data storage.Nowadays,the research of electric field control of magnetism is mainly concentrated in the composite multiferroic heterostructures with combined ferroelectricity,ferromagnetism and ferro-elasticity and magnetoelectric coupling effects.As one of the coupling mechanisms,the strain-mediated mechanism has been widely concerned in recent years because it is particularly convenient and effective at room temperature.So far,there are fewer electric control of magnetism researches for epitaxial ferromagnetic film.We chose Fe₈₁Ga₁₉ with large magnetostriction coefficient as ferromagnetic layer and Pb(Mg_1/3Nb_2/3)_0.7Ti_0.3O₃ with large piezoelectric coefficient as ferroelectric layer.In paper,Fe Ga films were deposited on Mg O（001）by magnetron sputtering system.The epitaxial relationship of Fe Ga（001）<110>//Mg O（001）<100>is characterized by x-ray diffraction.Magnetic hysteresis loops with one-step and two-step were showed by the longitudinal and transverse magneto-optical Kerr systems.In terms of Stoner-Wohlfarth model for Magnetic single domain,the angular dependence of magnetic switching fields is fitted well.Based on the magnetic research of epitaxial Fe Ga film,Fe Ga film were deposited on PMN-PT（001）by magnetron sputtering system.The preparation process of samples were mainly regulated by different growth temperatures.However,because the epitaxial grown for Fe Ga on PMN-PT is hard to be achieved due to tiny distortion of the pseudocubic lattice of PMN-PT.Finally,we chose to insert different thicknesses Mg O buffer layer between Fe Ga and PMN-PT for Fe Ga film epitaxial exploration.Comparing X-ray diffraction of Fe Ga samples with different thickness buffer layers,samples of the others Mg O buffer layer thickness indicate obviously Fe Ga（002）peaks,except the samples of 1 nm Mg O buffer layer.The epitaxial relationship of Fe Ga（001）<110>//Mg O（001）<100>//PMN-PT（001）<100>is characterized by x-ray diffraction and high-resolution transmission electron microscopy.Magnetic hysteresis loops with one-step and two-step were also showed by the longitudinal and transverse magneto-optical Kerr systems.In terms of Stoner-Wohlfarth model for Magnetic single domain,the angular dependence of magnetic switching fields is also fitted well.And the magnetic anisotropy structure of sample is further confirmed by Ferromagnetic resonance（FMR）.Based on in plane four-symmetry for the crystal structure and magnetic structure of sample,the magnetism of the sample is studied by electric field regulation.In comparison with virgin state,magnetic hysteresis loops is changed from the one-step to the two-step and the two-step to the three-step due to the effect of electric field,which indicates the magnetic reversal route is changed.By the research of the Ferroelectric（FE）domain switching of PMN-PT（001）with the applied of positive and negative electric field,109°Ferroelectric domain switching is crucial for the magnetic regulation of Fe Ga film.Based on the two magnetic anisotropy models under the action of electric field,the angular dependence of magnetic switching fields under the positive and negative electric field is also fitted well.With removed of electric field,the magnetism of film is changed due to the presence of residual stress.And the non-volatile regulation of magnetism is realized.The angular dependence of magnetic switching fields is fitted well when applied positive and negative electric field.The two magnetic anisotropy models are further confirmed by FMR after positive and negative polarization.The change of uniaxial anisotropy with electric field indicates that the strain-mediated mechanism is dominant.