Observation of Hydrogen-Induced Dzyaloshinskii-Moriya Interaction and Reversible Switching of Magnetic Chirality

Gong Chen,Andreas K Schmid,Roberto Lo Conte,Maccallum Robertson,Colin Ophus,Kai Liu,Markus Hoffmann,Roland Wiesendanger,Haifeng Ding,André L Fernandes Cauduro,Stefan Blügel

doi:10.1103/physrevx.11.021015

Abstract

The Dzyaloshinskii-Moriya interaction (DMI) has drawn great attention as it stabilizes magnetic chirality, with important implications in fundamental and applied research. This antisymmetric exchange interaction is induced by the broken inversion symmetry at interfaces or in non-centrosymmetric lattices. Significant interfacial DMI was found often at magnetic / heavy-metal interfaces with large spin-orbit coupling. Recent studies have shown promise of induced DMI at interfaces involving light elements such as carbon (graphene) or oxygen. Here we report direct observation of induced DMI by chemisorption of the lightest element, hydrogen, on a ferromagnetic layer at room temperature, which is supported by density functional theory calculations. We further demonstrate a reversible chirality transition of the magnetic domain walls due to the induced DMI via hydrogen chemisorption/desorption. These results shed new light on the understanding of DMI in low atomic number materials and design of novel chiral spintronics and magneto-ionic devices.

Highlights

The Dzyaloshinskii-Moriya interaction (DMI) is an antisymmetric exchange interaction, which can be induced in systems with broken inversion symmetry [1,2], such as the initially proposed Fe2O3 with weak ferrimagnetism, bulk materials with broken inversion symmetry like B20 compounds [3,4], or thin film systems [5,6]
When the multilayer has very weak Pd-like DMI, we discover a chirality transition of magnetic domain walls in the Ni=Co layers from lefthanded to right-handed upon hydrogen chemisorption, indicating that the chemisorbed hydrogen on top of the surfaces introduces finite DMI that favors right-handed chirality, which is supported by density functional theory (DFT) calculations
In the dissociative adsorption of molecular hydrogen used in this study, prior experimental work showed that the hydrogen atoms adsorb favorably on the top surface due to the presence of a chemisorption energy well [47,48], which is corroborated in more recent analyses using DFT for the case of Ni [49] and Co [50]

Summary

INTRODUCTION

The Dzyaloshinskii-Moriya interaction (DMI) is an antisymmetric exchange interaction, which can be induced in systems with broken inversion symmetry [1,2], such as the initially proposed Fe2O3 with weak ferrimagnetism, bulk materials with broken inversion symmetry like B20 compounds [3,4], or thin film systems [5,6]. Tan et al have demonstrated Hþ-based reversible magnetoionic switching at room temperature, where electric-fieldcontrolled hydrogen transport to the buried Co=GdO interface is used to toggle the perpendicular magnetic anisotropy (PMA) [40]. Such modifications of material properties through ionic motion are highly effective in tailoring interfacial characteristics and, physical and chemical properties [41,42,43,44,45,46]. Our results extend the picture of the interfacial DMI to the lightest element and enrich the hydrogen-related design of chiral spintronics and magneto-ionic devices

RESULTS AND DISCUSSION

Exploring interfacial DMI induced by chemisorbed hydrogen

Estimation of the strength of chemisorbed-hydrogen-induced DMI

Hydrogen-assisted reversible control of the chirality

CONCLUSION

Results