Stable humplike Hall effect and noncoplanar spin textures in SrRuO3 ultrathin films

Byungmin Sohn,Hwan Young Choi,Hua Zhou,Taeyang Choi,Changyoung Kim,Young Jai Choi,Seo Hyoung Chang,Bongju Kim,Alessandro Bombardi,Se Young Park,Jung Hoon Han,Dan G Porter,Jun Woo Choi,Jae Young Moon

doi:10.1103/physrevresearch.3.023232

Abstract

We observed a hump-like feature in Hall effects of SrRuO$_3$ ultrathin films, and systematically investigated it with controlling thicknesses, temperatures and magnetic fields. The hump-like feature is extremely stable, even surviving as a magnetic field is tilted by as much as 85$^\circ$. Based on the atomic-level structural analysis of a SrRuO$_3$ ultrathin film with a theoretical calculation, we reveal that atomic rumplings at the thin-film surface enhance Dzyaloshinskii-Moriya interaction, which can generate stable chiral spin textures and a hump-like Hall effect. Moreover, temperature dependent resonant X-ray measurements at Ru L-edge under a magnetic field showed that the intensity modulation of unexpected peaks was correlated with the hump region in the Hall effect. We verify that the two-dimensional property of ultrathin films generates stable non-coplanar spin textures having a magnetic order in a ferromagnetic oxide material.

Highlights

In magnetic materials, topological properties based on noncoplanar spin textures offer intriguing possibilities for exploring emergent properties and creating functionalities at the nanoscale
Based on a theoretical calculation and experimental observations, we suggest that the robust humplike structure in Hall resistivity is induced by noncoplanar spin textures, which can be stabilized by DzyaloshinskiiMoriya interaction (DMI) and strong out-of-plane magnetic anisotropy
The phase diagram exhibited the universal trend of the nontrivial topological phase in ferromagnetic films compared to previous reports on the SrRuO3/SrIrO3 heterostructure [16], the thin-film chiral magnet Fe1−xCoxSi [3], and FeGe [12]

Summary

INTRODUCTION

Topological properties based on noncoplanar spin textures offer intriguing possibilities for exploring emergent properties and creating functionalities at the nanoscale. The underlying design strategy for achieving stability has been artificially breaking the inversion symmetry and boosting the spin-orbit coupling necessary for DMI by exploiting the heterostructure of thin film with a heavy-metal layer [15]. Such heterostructures usually become quite complicated, which should be detrimental to construction of theoretical models and designing highly scalable energy efficient devices. Based on a theoretical calculation and experimental observations, we suggest that the robust humplike structure in Hall resistivity is induced by noncoplanar spin textures, which can be stabilized by DMI and strong out-of-plane magnetic anisotropy

Hall effect measurements

Cation rumpling on the surface

Experimental evidence for a notrivial magnetic order

SUMMARY