Quaternary-digital data storage based on magnetic bubbles in anisotropic materials

TL;DR

This paper introduces a novel quaternary data storage method using four types of magnetic bubbles in anisotropic materials, enabling stable, parallel-moving storage units for advanced racetrack memory devices.

Contribution

It demonstrates the coexistence and controllable movement of four distinct trivial magnetic bubbles in anisotropic materials, enabling quaternary data storage.

Findings

Four types of magnetic bubbles can coexist in anisotropic materials.

Bubbles can be written, distinguished, and moved parallel to currents.

The approach overcomes skyrmion limitations for racetrack memory.

Abstract

The topologically non-trivial nano-whirls, called magnetic skyrmions, are often considered attractive for spintronic applications like the racetrack data storage device. However, skyrmions do not move parallel to applied currents and typically do not coexist with other nano-objects, making the realization of such storage concepts difficult. Herein we consider materials with an anisotropic DMI, like tetragonal Heusler materials, and show that four distinct types of topologically trivial bubbles can coexist. We show that each of them can be written by spin torques and that they can be distinguished using a single magnetic tunneling junction. Due to their trivial topology, the four types of bubbles move parallel to applied electrical currents and remain equidistant under motion. Still, the bubbles have a small size and high stability comparable to topologically non-trivial spin textures. This allows to construct a quaternary-digit-based racetrack storage device that overcomes the two mentioned drawbacks of skyrmion-based racetracks.