Ferromagnetic resonance studies of surface and bulk spin-wave modes in a CoFe∕PtMn∕CoFe multilayer film

Abstract

We studied exchange-dominated surface and bulk spin-wave modes in a single period of CoFe/ PtMn/ CoFe trilayer film grown on a seed layer of Ru with CoFe film compositions being Co-16 at. % Fe. The thickness of the ferromagnetic CoFe layers is ϳ400 Å and that of the antiferromagnetic layer is 120 Å. Multimode spin-wave spectra were observed using the ferromagnetic resonance technique, as the sample plane was rotated with respect to the direction of the magnetic field. The effective magnetic anisotropy parameters and the g factor of the magnetic film were calculated from the field corresponding to the main ͑strongest͒ resonance peak at different angles. In addition, we identified a high-order standing spin wave in our spectra and found a "critical angle" in the multilayer sample. As H is significantly rotated away from the normal, there is a critical orientation where only a single acoustic spin-wave mode can be observed. We included an effective surface anisotropy field to describe our results. From the surface anisotropy, we are able to analyze the spin-wave resonance spectra in terms of the dynamic surface spin pinning. This allows us to determine the exchange interaction stiffness in the CoFe layers, J ϳ 2.7 meV.

Ultrafast optical study of spin wave resonance and relaxation in a CoFe/PtMn/CoFe trilayer film

“…Our values for the magnetic anisotropies and spin stiffness are in fairly good agreement with those from the FMR and VSM measurements. 5,6 In addition to SW E and SW 0 , SW D with significantly smaller intensity also contributes to our time resolved spectra. This mode is independent of external field and has a constant frequency of 3.1 GHz.…”

“…4 One such example is the Ru-seeded CoFe/PtMn/CoFe structure. 5,6 The high moment ferromagnetic ͑FM͒ CoFe thin films couple strongly with antiferromagnetic ͑AFM͒ PtMn layer, rendering a low hard axis coercivity of 2-4 Oe and a significant enhancement of in-plane anisotropy of ϳ57-123 Oe.…”

Spin-wave resonance frequency in a multi-layer film

“…5, different interface coupling can lead to different effects of the interface anisotropy on the SWR frequency. 16 Figure 9 shows the comparison of the SWR frequencies in symmetric bilayer and triple-layer films, these curves are chosen from Fig.3-8. From Fig.9, we can see that the SWR frequency of modes m=2, 3 and 4 decreases clearly with increasing thickness of the film.…”

“…The relation of the resonance field H n with the mode number n obeys the so-called n 2 law and the interlayer exchange constants were determined [15]. The exchange-dominated surface and bulk SWR spectra were studied in a single period of CoFe/PtMn/CoFe trilayer film [16]. An FMR study of sputtered Ru(7nm)/NiFe(t FM )/IrMn(6nm)/Ru(5nm) exchange-biased bilayers at X-and Q-band microwave frequencies reveals the excitation of spin-wave and NiFe resonance modes.…”

Determination of magnetic anisotropies, interlayer coupling, and magnetization relaxation in FeCoB/Cr/FeCoB

“…15 The materials provide a unique means to investigate the interfacial interaction and the exchange coupling. 16 Second, the FM/ AFM/FM structures can have their magnetic behaviors influenced by layer thickness, crystalline phase growth conditions, and strain between juxtaposed crystalline layers. Such influences affect magnetic ordering temperature, magnetic anisotropy, magnetic axis, and magnetic coupling of magnetic layers through a nonmagnetic or an AFM layer.…”