Origin of low-field microwave absorption in metallic magnetic films evidenced in FeRh/Ta/GaAs

Doan Ba Nguyen (1) , Giovanni Olivetti , Timothée Tremblais (1) , Isabella Boventer (2) , F. Vidal (1, 3) , Jean Eudes Duvauchelle (1, 3) , Catherine Gourdon (1, 3) , L. Thevenard (4, 1)

1 INSP - Institut des Nanosciences de Paris
2 Laboratoire Albert Fert (ex-UMPhy Unité mixte de physique CNRS/Thales)
3 INSP-E13 - Nanostructures : Élaboration, effets quantiques et magnétisme
4 INSP-E11 - Photons, Magnons et Technologies Quantiques

Performing ferromagnetic resonance (FMR) experiments on a polycrystalline FeRh (270nm)/Ta (100nm)/GaAs film, we evidence a low-field hysteretic signal, in addition to the usual non-hysteretic FMR absorption peaks. Its coercivity coincides with the static coercivity of the sample, which can be strongly tuned with temperature, thanks to the first order nature of the antiferromagnetic to ferromagnetic transition of FeRh.

The sample was made using a graded composition technique which allows to obtain the Fe/Rh stoechiometry required for the presence of an antiferromagnetic-ferromagnetic transition. We show that the low-field microwave absorption (LFMA) signal can be well modelled by simply introducing the hysteresis of the static magnetization in the dynamic magnetic susceptibility. Finally, previous observations of LFMA on a cobalt thin film are also reproduced by this model. 55 Up to now, none of these studies had explored the low-field 56 range necessary to evidence LFMA experimentally. We fill 57 this gap by performing field-swept FMR at various temper-58 atures. Clear LFMA signals are obtained up to 25 GHz. We 59 show that taking into account the hysteresis in the usual Polder 60 susceptibility is sufficient to reproduce the important features 61 of our data, as well as that of previous authors[24]. This pro-62 vides a definitive explanation for the up-to-now elusive origins 63 of the LFMA phenomenon.

Mots clés: Ferromagnetic resonance; FeRh; sputtering

Domaines: Physique [physics]

Doan Ba Nguyen, Giovanni Olivetti, Timothée Tremblais, Isabella Boventer, F. Vidal, et al.. Origin of low-field microwave absorption in metallic magnetic films evidenced in FeRh/Ta/GaAs. 2024. ⟨hal-04709395⟩