Reduced effective magnetization and damping by slowly-relaxing impurities in strained $γ$-$\mathrm{Fe_2O_3}$ thin films

Manuel Müller; Monika Scheufele; Janine Gückelhorn; Luis Flacke; Mathias Weiler; Hans Huebl; Stephan Geprägs; Rudolf Gross; Matthias Althammer

doi:10.1063/5.0128596

paper

Reduced effective magnetization and damping by slowly-relaxing impurities in strained $γ$ - $F e_{2} O_{3}$ thin films

arXiv:2204.11498 · doi:10.1063/5.0128596

Abstract

We study the static and dynamic magnetic properties of epitaxially strained $γ$ - $F e_{2} O_{3}$ (maghemite) thin films grown via pulsed-laser deposition on MgO substrates by SQUID magnetometry and cryogenic broadband ferromagnetic resonance experiments. SQUID magnetometry measurements reveal hysteretic magnetization curves for magnetic fields applied both in- and out of the sample plane. From the magnetization dynamics of our thin films, we find a small negative effective magnetization in agreement with a strain induced perpendicular magnetic anisotropy. Moreover, we observe a non-linear evolution of the ferromagnetic resonance-linewidth as function of the microwave frequency and explain this finding with a model based on slowly relaxing impurities, the so-called slow relaxor model. By investigating the magnetization dynamics in our maghemite thin films as a function of frequency and temperature, we can isolate the temperature dependent contribution of the slowly relaxing impurities to the resonance linewidth and, in particular, observe a sign change in the effective magnetization. This finding provides evidence for a transition of the magnetic anisotropy from a perpendicular easy axis to an easy in-plane anisotropy for reduced temperatures.

arXiv comment10 pages, 8 figures

Reduced effective magnetization and damping by slowly-relaxing impurities in strained γ-Fe2​O3​ thin films

Abstract

References in corpus (12)

Reduced effective magnetization and damping by slowly-relaxing impurities in strained $γ$ - $F e_{2} O_{3}$ thin films