Structural origins of magnetic anisotropy in sputtered amorphous Tb-Fe films
TL;DR: Using x-ray-absorption fine-structure measurements, clear evidence is obtained for structural anisotropy in amorphous sputter-deposited TbFe films exhibiting perpendicular magnetic an isotropy.
Abstract: Using x-ray-absorption fine-structure measurements we have obtained clear evidence for structural anisotropy in amorphous sputter-deposited TbFe films exhibiting perpendicular magnetic anisotropy. Modeling of the data shows that perpendicular anisotropy in these films is associated with Fe-Fe and Tb-Tb pair correlations which are greater in plane and Tb-Fe correlations which are greater perpendicular to the film plane. Upon annealing at 300 \ifmmode^\circ\else\textdegree\fi{}C the measured structural anisotropy disappears and the magnetic anisotropy decreases to a level consistent with magnetoelastic interactions between the film and substrate.
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TL;DR: A composition gradient is found to provide the necessary structural inversion asymmetry for a bulk Dzyaloshinskii–Moriya interaction to manifest itself in GdFeCo amorphous ferrimagnets.
Abstract: Symmetry breaking is a fundamental concept that prevails in many branches of physics1–5. In magnetic materials, broken inversion symmetry induces the Dzyaloshinskii–Moriya interaction (DMI), which results in fascinating physical behaviours6–14 with the potential for application in future spintronic devices15–17. Here, we report the observation of a bulk DMI in GdFeCo amorphous ferrimagnets. The DMI is found to increase linearly with an increasing thickness of the ferrimagnetic layer, which is a clear signature of the bulk nature of DMI. We also found that the DMI is independent of the interface between the heavy metal and ferrimagnetic layer. This bulk DMI is attributed to an asymmetric distribution of the elemental content in the GdFeCo layer, with spatial inversion symmetry broken throughout the layer. We expect that our experimental identification of a bulk DMI will open up additional possibilities to exploit this interaction in a wide range of materials. A composition gradient is found to provide the necessary structural inversion asymmetry for a bulk Dzyaloshinskii–Moriya interaction to manifest itself.
118 citations
TL;DR: In this article, the authors provide a comprehensive review of recent progress in SOT in various materials, including both spin sources and magnetic functional layers, and discuss its promising applications for nonvolatile SOT-magnetic random access memory and other device configurations.
117 citations
TL;DR: In this article, a brief overview of PMA materials for two important data storage applications, namely perpendicular recording and MRAM, is presented, where the major requirements, challenges and future prospects of these materials for future STT-MRAM devices are discussed.
113 citations
TL;DR: In this paper, the influence of the film thickness (5 - 85 nm) on the sample magnetic properties was investigated in a wide composition range between 15 at% and 38 at.% of Tb.
Abstract: Ferrimagnetic rare earth - transition metal Tb-Fe alloy thin films exhibit a variety of different magnetic properties, which depends strongly on composition and temperature. In this study, first the influence of the film thickness (5 - 85 nm) on the sample magnetic properties was investigated in a wide composition range between 15 at.% and 38 at.% of Tb. From our results, we find that the compensation point, remanent magnetization, and magnetic anisotropy of the Tb-Fe films depend not only on the composition but also on the thickness of the magnetic film up to a critical thickness of about 20-30 nm. Beyond this critical thickness, only slight changes in magnetic properties are observed. This behavior can be attributed to a growth-induced modification of the microstructure of the amorphous films, which affects the short range order. As a result, a more collinear alignment of the distributed magnetic moments of Tb along the out-of-plane direction with film thickness is obtained. This increasing contribution of the Tb sublattice magnetization to the total sample magnetization is equivalent to a sample becoming richer in Tb and can be referred to as an “effective” composition. Furthermore, the possibility of all-optical switching, where the magnetization orientation of Tb-Fe can be reversed solely by circularly polarized laser pulses, was analyzed for a broad range of compositions and film thicknesses and correlated to the underlying magnetic properties.
85 citations