| The magnetic heterojunction comprised by magnetic materials and the other materi-als provides an excellent platform to investigate the magnetoelectric transport properties,interface coupling phenomenons and exotic quantum effects.Meanwhile,the relevant material structures are also the central part of spin functional devices,so it has become a hot-spot issue in condensed matter physics and electronic devices.The interface phe-nomenons and the interactions of heterojunction structures attach great significance for cutting-edge research.More importantly,the design and construct functional devices based on the transport characteristics of heterojunction is the prerequisite for industrial application.In this dissertation,we have accomplished the following research works re-volving around the coupling and transport properties of magnetic heterojunction,which includes the fabrication of the heterojunction,the investigations of transport properties and the characterization of the ultrafast spin transport.We have also constructured the mi-crowave device and terahertz emitter,the device characteristics and internal mechanism of device are studied in-depth.The main research results are summarized as follows:Ⅰ.The magnetic heterojunction comprised by intrinsic antiferromagnetic topological insulator and topological insulator（Mn Bi2Te4/Bi2Te3）has been designed and fabricated.We characterize the growth quality and atomic lattice of the heterojunction by using the high energy electron diffraction,X-ray diffraction,Raman scattering,atomic force mi-croscopy and scanning electron transmission microscopy.By optimizing the growth con-ditions continuously,the magnetic topological insulator heterojunctions with controllable thickness have been successfully deposited.The magnetoelectric transport properties of heterojunction have been systematically investigated by using physical property measure-ment system,we have observed a typical magnetic proximity coupling effect from both layers combined together and verified the concurrence of hybrid anomalous Hall effect from intrinsic Mn Bi2Te4layer and adjacent Bi2Te3layer.The resulting magnetic proxim-ity effect can be quantified by a classical molecular field model,and the related properties of exchange coupling in heterojunction has been analyzed by combining the temperature-dependent measurements.Ⅱ.A ionic liquid device based on the heterojunction of Mn Bi2Te4and Bi2Te3has been proposed and fabricated.With the help of the double electric layer structure formed by ionic liquid at the interface of heterojunction,we achevied the purpose of applying large electric field intensity with small applied voltage.We have effectively controlled the magnetoelectric transport properties and anomalous Hall signal of the heterojunction,the variations of the magnetoelectric transport behaviors are clearly shown by means of parameter extraction and comparison.By adding an effective calculation,the variation of carriers density of heterojunction is analyzed in-depth.Finally,the band structure of the heterojunction is qualitatively analyzed.Ⅲ.The spin transfer nano-oscillator comprised by the magnetic heterojunction of Pt/Ni Fe was constructure and proposed.The existence of radial vortex in the presence of interfacial Dzyaloshinskii-Moriya interaction is theoretically verified.At the same time,the radial vortex state can be brought into persistent self-oscillatory periodic motion by applying spin polarized current in a nanocontact cylinder magnetic multilayers struc-ture,Using micromagnetic simulation,the potential application for microwave emission is confirmed,and the threshold current density of radial vortex oscillator is one order of magnitude lower than traditional spin-torque nano-oscillators.Meanwhile,we have systematically studied the influence of current density and the electrode dimension on microwave emission properties.Ⅳ.The spintronic terahertz emitter consisting of the Ir Mn3/Ni Fe heterojunction has been designed and fabricated.A femtosecond spin current pulse is generated in the thin film of Ni Fe layer when it absorbs a femtosecond laser pulse,then the spin current is con-verted into transient charge current by the metallic Ir Mn3layer in picosecond timescales by means of inverse spin Hall effect.We timely record the terahertz emission associated with this ultrafast conversion process by means of electrooptic sampling,the spin terahertz source comprised by Ir Mn3/Ni Fe is verified.The mechanism of ultra-fast spin-to-charge conversion and terahertz emission in the heterojunction were clarified by comparing the magnetic materials and the heterojunction materials.Furthermore,the effects of incident power,incident direction and polarization direction of femtosecond laser on the perfor-mance of terahertz emission were studied systematically.Besides,the spin-to-charge con-version effciency of Ir Mn3/Ni Fe heterojunction is determined via quantitative analysis of the spin torque ferromagnetic resonance results. |
