Mode Structures and Damping of Quantized Spin Waves in Ferromagnetic Nanowires

Magnonic devices based on spin waves are considered as a new generation of energy-efficient and high-speed devices for storage and processing of information.Here we experimentally demonstrate that three distinct dominated magneto-dynamic modes are excited simultaneously and coexist in a transversely magnetized ferromagnetic wire by the ferromagnetic resonance(FMR)technique.Besides the uniform FMR mode,the spin-wave well mode,the backward volume magnetostatic spin-wave mode,and the perpendicular standing spin-wave mode are experimentally observed and further confirmed with more detailed spatial profiles by micromagnetic simulation.Furthermore,our experimental approach can also access and reveal damping coefficients of these spin-wave modes,which provides essential information for development of magnonic devices in the future.

Spin transport in epitaxial Fe3O4/GaAs lateral structured devices

Research in the spintronics community has been intensively stimulated by the proposal of the spin field-effect transistor(SFET),which has the potential for combining the data storage and process in a single device.Here we report the spin dependent transport on a Fe_(3)O_(4)/GaAs based lateral structured device.Parallel and antiparallel states of two Fe_(3)O_(4) electrodes are achieved.A clear MR loop shows the perfect butterfly shape at room temperature,of which the intensity decreases with the reducing current,showing the strong bias dependence.Understanding the spin-dependent transport properties in this architecture has strong implication in further development of the spintronic devices for room-temperature SFETs.

Timescales and contribution of heating and helicity effect in helicity-dependent all-optical switching

The heating and helicity effects induced by circularly polarized laser excitation are entangled in the helicity-dependent all-optical switching(HD-AOS),which hinders understanding the magnetization dynamics involved.Here,applying a dual-pump laser excitation,first with a linearly polarized(LP) laser pulse followed by a circularly polarized(CP) laser pulse,the timescales and contribution from heating and helicity effects in HD-AOS were identified with a Pt/Co/Pt triple-layer.When the LP laser pulses preheat the sample to a nearly fully demagnetized state,the CP laser pulses with a power reduced by 80% switch the sample’s magnetization.By varying the time delay between the two pump pulses,the results show that the helicity effect,which gives rise to the deterministic helicity-induced switching,arises almost instantly within 200 fs close to the pulse width upon laser excitation.The results reveal that the transient magnetization state upon which CP laser pulses impinge is the key factor for achieving HD-AOS,and importantly,the tunability between heating and helicity effects with the unique dualpump laser excitation approach will enable HD-AOS in a wide range of magnetic material systems having wideranging implications for potential ultrafast spintronics applications.