High Frequency Properties And Magnetoelectric Coupling Of Facing-Target Sputtered Epitaxial ?'-Fe₄N Films

It is important to realize the memory with low energy consumption,high speed and high density in spintronic devices.?'-Fe₄N is a promising material to be put into application due to its high spin polarization and chemical stability.In this dissertation,the epitaxial?'-Fe₄N films are fabricated on different substrates by facing-target magnetron sputtering,where the high-frequency properties and magnetoelectric coupling are studied in detail.The high-frequency properties of?'-Fe₄N films are investigated.Epitaxial?'-Fe₄N films with different thicknesses are fabricated on Mg O,Sr Ti O₃ and La Al O₃substrates by facing-target magnetron sputtering.The structural and physical properties are characterized by atomic force microscope,X-ray diffraction and high-resolution transmission electron microscope.It is proved that although the lattice mismatches between?'-Fe₄N and the substrates are-9.92%,-2.81%and 0.13%,where?'-Fe₄N films are highly epitaxial with quite low surface roughness due to the strain release from the misfit dislocations at the interface.Furthermore,the high frequency properties of all the films are studied by ferromagnetic resonance measurement system.It is found that the two-magnon scattering plays a dominant role in broadening the linewidth of?'-Fe₄N films.The Gilbert damping constant is about0.0135.The magnetoelectric coupling in?'-Fe₄N/PMN-PT multiferroic heterostructures is studied.?'-Fe₄N films with different thicknesses are fabricated on PMN-PT(001)and(011)substrates.The in-plane and out-of-plane magnetization and ferromagnetic resonance field at different electric fields are studied.It is found that the magnitude of the electric-field control on hysteresis loops of the samples first increases and then decreases as the?'-Fe₄N film thickness increases,which reaches its maximum at?'-Fe₄N film thickness of 17 nm.The magnetization modulation by electric field is as large as 1430%,which is much larger than the previous results.The control of the resonance field also arrives at 700 Oe.The magnetoelectric coupling in?'-Fe₄N/PMN-PT heterostructure is induced by the interfacial spin-dependent screening effect.