X. Ya

Interferometric properties of standing spin waves and the application to a phase comparator

We numerically studied the material and structural parameter dependence of interferometric properties of the standing spin wave resonance (SSWR) by micromagnetic simulations and demonstrate the feasibility of practical application to an integrated phase comparator. The micromagnetic configuration of the synthesized SSWR emitted from the two microwave currents flowing through the parallel strip lines depends on the phase difference Δϕ between them. Resultantly, the Δϕ is converted to the related output voltage with an overlaid phase detector, inductively coupled to the magnetic strip. Among the investigated various material systems, low damping (α ∼ 0.001) metallic ferromagnets are found to exhibit superior device performance due to the reduced viscous dissipation.

Controlling of voltage-induced spin wave resonance properties in ferromagnetic nanowires with perpendicular anisotropy

The voltage-induced manipulation of magnetic properties, including the modulation of coercively or the magnetization switching, has been attracting intense research interests [1].

Numerical analysis on spin dynamics in multilayer nanodots with interlayer antiferromagnetic coupling

Interlayer antiferromagnetic coupling have been attracting intense research interests, which is now exploring a new approach for drastic improvement in various spintronics devices.

Effect of distance between a magnet layer and an excitation antenna on the nonreciprocity of magnetostatic surface waves

We investigated the effect of the distance between a magnetic layer and an excitation antenna on the nonreciprocity of magnetostatic surface waves (MSSWs), using devices with various thicknesses of the SiO2 layer (t SiO2) to isolate an antenna from a permalloy layer. The nonreciprocity of MSSWs increases with increasing t SiO2. This increase in MSSW nonreciprocity is caused by an increase in the ratio of the MSSW excitation efficiency of the out-of-plane component of a microwave field to that of the in-plane component of a microwave field. Thus, we found that the nonreciprocity of MSSWs can be controlled by a very simple method.

Standing spin wave resonant properties of spin-twist structure in exchange coupled composite films

In the present study, a spin-twist structure embedded in an exchange coupled hard/soft/hard tri-layer system was proposed as a novel spin wave (SW) guide. Details of spin wave dynamics was comparatively analyzed for tri-layers with various layer thicknesses and the inter-layer exchange coupling. The practical performance as a wave guide was optimized in terms of SW resonance frequency and the expected inductive output, both of them were successfully improved by integrating the merit of individual layers through dual exchange bias effects.

Numerical analysis of inductive detection of magnetic vortex motion excited with circularly polarized field

In the present study, the rotation and switching of a vortex core in submicron-size square dots were numerically analyzed by micromagnetic simulation. This study clarified that the eigenfrequency of the vortex core is strongly dependent on the magnetostatic energy and that rapid switching can be realized by circularly polarized fields with practical amplitudes at the corresponding eigenfrequency. The inductive detection of vortex core rotation, which can distinguish vortex core polarity, was successfully demonstrated and the structural design of the detector was optimized.

Numerical analysis on two dimensional standing spin waves in microstructured exchange-coupled hard/soft bilayer strips

This study reports micromagnetic simulations of the dynamics of standing spin waves in microstructured hard-soft bilayers. It is found that the standing spin wave resonance property can be continuously varied with layer thickness ratio. Numerical results demonstrate feasibility of the microstructured hard-soft bilayer strips for the integrated spin wave devices, where the thickness ratio of the exchange coupled hard-soft bilayer can be a structural design parameter.

Controlling of synthesized standing spin wave configuration with external fields

Lateral spin waves (SWs) propagating along the ferromagnetic wave guide have been attracting intense research interests due to potential ability for future device applications, including SW based logic devices or signal processing devices, where the phase of SW is utilized as a state variable [1-3]. Geometrically confined standing spin wave (SSW) [4,5] is promising for down sizing and power saving of the SW based devices, since the input microwave power is efficiently utilized for the SW excitation. In the present study, controlling of the SSW configurations in microstructured permalloy strips has been systematically investigated by electrical measurements with various artificial modurations and micromagnetic simulations. A promising application of the observed results to field programmable SW based devices was also discussed.

Microwave assisted spin transfer torque switching in a vertically integrated logic-in-memory architecture

An exchange coupled multilayer stack, proposed as a quarterly state logic-in-memory structure, is presented in this study. Fundamental device operations have been numerically demonstrated with micromagnetic simulations. Results confirm the frequency dependence of magnetization reversal in high density magnetic recording.

Microwave-Assisted Spin-Transfer Torque Switching in a Vertically Integrated Architecture

We propose an exchange-coupled trilayer system as a quarterly state structure. Fundamental device operations have been numerically demonstrated with micromagnetic simulations. Cooperative data writing scheme with the dual spin-transfer torque and radio frequency magnetic fields was demonstrated. Dependence of the perpendicular spin-wave resonant spectroscopy on the magnetization state in the trilayer was utilized as a read-out principle.