Study On Spin-wave Logic Devices Based On Magnetic Domain-wall

With the continuous miniaturization of integrated circuits,the development of traditional microelectronic devices has encountered technical bottlenecks.Once the scale of the devices with electrons as information carriers reaches nanometer scale,the energy loss on information processing and transmission will be unbearable.Therefore,it is necessary to find a new device matching the requirements of future information technology.Among a lot of candidates,magnonic devices based on spin waves,with the characteristics of nanoscale size,low energy loss and high speed,are powerful competitors for new generation of nano-devices.In this thesis,a novel waveguide based on bilayer magnetic thin film is designed by means of micromagnetic simulation.This waveguide forms Bloch-type domain walls,where spin waves can propagate,through exchange-coupling effect.According to detailed study of its transmission characteristics,XNOR and NOT magnonic logic gate are designed based on this waveguide.Firstly,the model based on soft/hard magnetic bilayer film is built by micromagnetic simulation.Then,the waveguide has a magnetic structure with out-of-plane magnetic moments through external magnetic field.After removing the external magnetic field,the soft magnetic layer will form a stable Bloch-type domain wall through the exchangecoupling effect between the hard magnetic layer and the soft magnetic layer.Next,a sinusoidal pulse field is applied to the waveguide.Then,the dispersion relation of spin wave is obtained by 2D Fourier transformation.According to the dispersion relation,the spin waves excited below 80 GHz can be conducted confined in the domain-wall channel of the waveguide as one-mode backward volume wave.In order to further study the transmission characteristics of spin waves in the domain-wall channel,the transmissioin process of 25 GHz spin wave conducted in the channel is simulated.Then,the simulation results show that the transmission speed of the spin wave is 1.72km/s,and the width of the domain-wall channel is 18.2nm.Compared with Néel-type domain-wall magnonic waveguide,its spin-wave transmission speed is faster and its transmission channel is narrower.The new characteristics provide a new possible method to design nanoscale magnonic devices with high spin-wave transmission speed.On the other hand,based on the study of Bloch-type domain-wall waveguide,novel XNOR and NOT magnonic logic gate are designed.This device is realized by spin-wave phase shift through voltage modulation.It uses voltage to change the interfacial magnetic anisotropy of magnetic materials,so that the phase of spin waves can be shifted by the change of effective field.By means of micromagnetic simulation,it is showed that the spin wave can be successfully shifted ? phase when it gets through a 800-nm-long region with a 1.4V applied voltage.This phase modulation method make devices operated simply and control easily.At last,this phase shifted mechanism is applied to design magnonic logic devices.And the transmission characteristics of the Bloch-type domainwall waveguide are used to make spin waves to interfere with each other which leading to spin-wave output with different amplitude.Finally,we obtain the spin-wave logic devices with the functionality of XNOR gate and NOT gate.