Anatomy of Dzyaloshinskii-Moriya Interaction at Co/Pt Interfaces (1501.05511v1)

Abstract: The Dzyaloshinskii-Moriya Interaction (DMI) between spins is induced by spin-orbit coupling in magnetic materials lacking inversion symmetry. DMI is recognized to play a crucial role at the interface between ferromagnetic (FM) and heavy nonmagnetic (NM) metals to create topological textures called magnetic skyrmions which are very attractive for ultra-dense information storage and spintronic devices. DMI also plays an essential role for fast domain wall (DW) dynamics driven by spin-orbit torques. Here, we present first principles calculations which clarify the main features and microscopic mechanisms of DMI in Co/Pt bilayers. DMI is found to be predominantly located at the interfacial Co layer, originating from spin-orbit energy provided by the adjacent NM layer. Furthermore, no direct correlation is found between DMI and proximity induced magnetism in Pt. These results clarify underlying mechanisms of DMI at FM/NM bilayers and should help optimizing material combinations for skyrmion- and DW-based storage and memory devices.

• The paper shows that DMI is predominantly localized at the interfacial Co layer, driven by Pt’s spin–orbit coupling to stabilize skyrmions and enhance domain wall motion.
• The study finds that proximity-induced magnetism in Pt has negligible influence on DMI, with calculated strengths ranging from 1.5 to 3 meV and displaying anticlockwise chirality.
• By comparing Co/Pt with other metal interfaces, the research predicts chirality reversal effects and suggests design pathways for optimizing spintronic devices.

Analysis of Dzyaloshinskii-Moriya Interaction in Co/Pt Interfaces

The paper titled "Anatomy of Dzyaloshinskii-Moriya Interaction at Co/Pt Interfaces" by Yang et al. undertakes a rigorous theoretical examination of the Dzyaloshinskii-Moriya Interaction (DMI) within cobalt/platinum (Co/Pt) bilayers, pivotal for applications in spintronics technology. This research primarily employs first-principles calculations to elucidate the characteristics and fundamental mechanisms underpinning DMI in these heterostructures.

Key Findings

The authors report several critical insights from their computational investigation:

1. Localization of DMI: It is determined that the DMI is predominantly concentrated at the interfacial Co layer. The DMI originates from the spin-orbit coupling (SOC) facilitated by the adjacent Pt layer. This distribution is essential for stabilizing topological magnetic textures such as skyrmions and enabling fast domain wall (DW) motion.
2. Negligible Influence of Proximity-Induced Magnetism: Contrary to some hypotheses suggesting direct correlation, the paper finds no significant link between DMI and proximity-induced magnetism within Pt. This conclusion is substantiated by calculations showing an inverse relationship between the Pt magnetic moment and DMI strength.
3. DMI Strength and Chirality: The research quantifies the total DMI strength in Co/Pt bilayers, presenting values ranging from 1.5 to 3 meV. This significant strength, characterized by anticlockwise chirality, points to its potential utility in skyrmion-based storage applications.
4. Variation Across Metal Interfaces: By contrasting Co/Pt with other systems like Co/Pd and Co/Au, the paper affirms that the larger SOC in Pt compared to Pd and the absence of d states at the Fermi level in Au are critical factors for the observed differences in DMI magnitude and chirality.
5. Chirality Reversal Effects: The paper extends to Co/Ir and Fe/Ir interfaces, noting the difference in DMI chiralities, thereby predicting notable effects when combining Pt and Ir layers on either side of Co layers.

Implications and Future Directions

The findings of this research have considerable implications for spintronic devices, particularly in the advancement of high-density data storage technologies. Understanding the DMI’s localization and behavior at the atomic level aids in optimizing materials for better performance of skyrmion-based devices and DW dynamics. The computational methodology outlined provides a robust framework for predicting DMI characteristics across various material systems, thereby guiding experimental efforts in material synthesis and heterostructure engineering.

In future explorations, extending this computational approach to more complex multilayer systems could yield insights into interactions between different ferromagnetic and non-magnetic metallic layers, potentially unveiling new functional properties. Additionally, further analysis of the role of interface mixing and its effect on chiral magnetic structures could inform strategies to mitigate detrimental mixing effects observed in industrial processes.

Conclusion

This paper comprehensively dissects the origins and mechanisms of DMI in Co/Pt interfaces, advancing our comprehension of spintronic material behavior. The research not only provides vital data on DMI characteristics but also sets the stage for novel developments in skyrmion technologies and next-generation data storage solutions. The investigation’s contributions are poised to have profound impacts on spintronics research and technological innovation.