Rotatable anisotropy on ferromagnetic/antiferromagnetic bilayer investigated by Brillouin light scattering

Abstract

The nature of the rotatable anisotropy in ferromagnetic/antiferromagnetic (FM/AF) NiFe/IrMn bilayers has been investigated using magneto-optical Kerr effect magnetometry, ferromagnetic resonance, and Brillouin Light Scattering (BLS) techniques. The behavior of the magnon frequencies with an external magnetic field applied in the bilayer plane has been measured by BLS. The angular dependence of magnon frequency shows a shift when compared to numerical calculation for different magnetic field intensities. This frequency shift can be associated with the rotatable anisotropy and it depends on the magnetic field intensity. As a result, the rotatable anisotropy field exhibits a non-monotonic dependence on the applied field. The results are interpreted considering the coexistence of parallel and antiparallel coupling at the FM/AF interface.

Theoretical investigation of ferromagnetic resonance in a ferromagnetic thin film with external stress anisotropy

“…Recently, several methods have been used to research the single, bilayers and multilayers of ferromagnetic film, such as ferromagnetic resonance (FMR) [1][2][3][4][5] and Brillouin light scattering. [6][7][8] Ferromagnetic resonance is a powerful tool for quantitative determination of the properties of magnetic materials, such as magnetic anisotropies and relaxation, [9,10] magnetic coupling, [11,12] linewidth, [13][14][15][16] and others. However, in these studies, most of the investigations only take into account interlayer coupling and exchange bias.…”

Polycrystalline exchange-biased bilayers: magnetically effective vs. structural antiferromagnetic grain volume distribution

“…One -to the knowledge of the authors -hitherto unanswered question is, whether the structural GVD is identical to the distribution of the magnetically active AF grain volumes. Therefore, a quantitative link between the magnetic characteristics of polycrystalline AF/F-bilayers and their microstructure is crucial, even if the connection between thickness-dependent relations of H EB and H C and the AF layer's granular characteristic, or the nature of the EB as an interface effect itself, can be reasoned [3,[29][30][31][32][33].…”

Modulation of interfacial magnetic relaxation timeframes by partially uncoupled exchange bias

“…In addition to FMR, high-frequency magnetization behavior can be characterized by Brillouin light scattering technique (BLS). In this case, the exchange bias is manifested as frequency variations for both Stokes and anti-Stokes lines as well as changes in dispersion relations [10,41,42]. The feature of BLS is that it detects spin waves on the surface of a ferromagnetic layer nearest to a light incidence point [10,41,42].…”

“…In this case, the exchange bias is manifested as frequency variations for both Stokes and anti-Stokes lines as well as changes in dispersion relations [10,41,42]. The feature of BLS is that it detects spin waves on the surface of a ferromagnetic layer nearest to a light incidence point [10,41,42]. For exchange biased FM-AFM thin films, this surface contacts directly with the adjacent AFM layer and, therefore, the BLS technique can be applied to analyze the interfacial FM and AFM grains contributions to spin-dynamics in the FM layer [42,43].…”

“…The feature of BLS is that it detects spin waves on the surface of a ferromagnetic layer nearest to a light incidence point [10,41,42]. For exchange biased FM-AFM thin films, this surface contacts directly with the adjacent AFM layer and, therefore, the BLS technique can be applied to analyze the interfacial FM and AFM grains contributions to spin-dynamics in the FM layer [42,43]. Thus, it looks promising to apply FMR and BLS as complementary experimental techniques for assessment of both the bulk and interfacial magnetic anisotropies contributing to the exchange bias.…”