Topological Hall Effect and Skyrmion-like Bubbles at a Charge-transfer Interface

TL;DR

This study investigates the emergence and control of topological Hall effects and Skyrmion-like magnetic bubbles at a charge-transfer interface in a trilayer structure, with implications for spintronic memory devices.

Contribution

It provides detailed analysis of the topological Hall effect, identifies conditions for Skyrmion-like bubbles, and demonstrates their manipulation and low-current mobility at a charge-transfer interface.

Findings

Hump-shaped Hall signal indicates Skyrmion-like bubbles.

Optimal layer thicknesses tune charge transfer and bubble formation.

Low threshold current enables bubble motion, promising for spintronics.

Abstract

Exploring exotic interface magnetism due to charge transfer and strong spin-orbit coupling has profound application in future development of spintronic memory. Here, the emergence, tuning and interpretation of hump-shape Hall Effect from a CaMnO3/CaIrO3/CaMnO3 trilayer structure are studied in detail. The hump signal can be recognized as Topological Hall Effect suggesting the presence of Skyrmion-like magnetic bubbles; but the debated alternative interpretation where the signal being an artefact between two cancelling Anomalous Hall Effect loops is also discussed. Firstly, by tilting the magnetic field direction, the evolution of Hall signal suggests transformation of the bubbles topology into a more trivial kind. Secondly, by varying the thickness of CaMnO3, the optimal thicknesses for the hump signal emergence are found, suggesting a tuning of charge transfer fraction. Using high-resolution transmission electron microscopy, a stacking fault is also identified, which distinguishes the top and bottom CaMnO3/CaIrO3 interfaces in terms of charge transfer fraction and possible interfacial Dzyaloshinskii-Moriya Interaction. Finally, a spin-transfer torque experiment revealed a low threshold current density of ~10^9 A/m^2 for initiating the motion of bubbles. This discovery opens a possible route for integrating Skyrmions with antiferromagnetic spintronics.