Controlling of Standing Spin Wave Configuration in Nanowires with Domain Wall

Spin dynamics in nanostructured magnetic system have attracting intense research interests from view point of fundamental physics and practical applications. The geometrically confined standing spin wave resonance (SSWR) is one of the most power efficient excitation modes. Various kinds of SSWR modes have been observed in wires [1], squares [2] and rectangular dots [3], made of in-plane magnetization films. In the present study, the SSWR properties of nanowires with perpendicular anisotropy have been numerically investigated. Especially, the effect of the domain wall (DW) on the SSWR is focused, aiming at the application to a novel memory and logic applications. Fig. 1 (a) presents a designed device structure, consists of a nanowire and inductively coupled conductors for the SWs generators (GE1, GE2) and detector (DE). Material parameters of large perpendicular and low damping ferromagnets, such as MnGa, MnAl, were assumed in the micromagnetic simulations: M_s = 1000 emu/cm³, H_k = 13 kOe, α= 0.01. Pulsed microwave currents with phase lag δφ = π and the duration of 930 ps (37.2 ps (=1/(26.9 GHz)) × 25 periods) were assumed to be applied through GE1 and GE2, which excite the 2nd mode SSW along the nanowire. The inductive output waveform when the DW located at the nanowire center is shown as Fig. 1(b). The maximum amplitude V_out computed for various locations of the DW (xDW) is shown in Fig. 2(a). The significant dependence of the V_out reflects the modification of the SSW configuration due to the DW location, as shown in Fig. 2(b), (c). The DW located under the GE locally suppresses the magnetization precession, reflecting lower V_out, while the influence from the DW located at the nanowire center (node of the SSW) is subtle, reflecting higher V_out. The obtained numerical results demonstrate feasibility of the domain wall location as a state variable of nanowires.