Nanoscale magnetic bubbles in Nd2Fe14B at room temperature

Yangkun He,Toni Helm,Claudia Felser,Johannes Kroder,Rudolf Schaefer,Walter Schnelle,Abhay Kant Srivastava,Ankit Kumar Sharma,Darius Pohl,Sebastian Schneider,Gerhard H Fecher,Bernd Rellinghaus,Ivan Soldatov,Stuart S P Parkin

doi:10.1103/physrevb.105.064426

Abstract

The increasing demand for computer data storage with a higher recording density can be addressed by using smaller magnetic objects, such as bubble domains. Small bubbles predominantly require a strong saturation magnetization combined with a large magnetocrystalline anisotropy to resist self-demagnetization. These conditions are well satisfied for highly anisotropic materials. Here, we study the domain structure of thin ${\mathrm{Nd}}_{2}{\mathrm{Fe}}_{14}\mathrm{B}$ lamellae. Magnetic bubbles with a minimum diameter of 74 nm were observed at room temperature, approaching even the range of magnetic skyrmions. The stripe domain width and the bubble size are both thickness dependent. Furthermore, a kind of bubble was observed below the spin-reorientation transition temperature that combine bubbles with opposite helicity. In this paper, we reveal ${\mathrm{Nd}}_{2}{\mathrm{Fe}}_{14}\mathrm{B}$ to be a good candidate for a high-density magnetic bubble-based memory.

Highlights

Magnetic bubbles are small magnetized cylindrical volumes in magnetic films with uniaxial, perpendicular magnetocrystalline anisotropy that can be used for computer data storage [1]
Magnetic bubbles with a minimum diameter of 74 nm were observed at room temperature, approaching even the range of magnetic skyrmions
We reveal Nd2Fe14B to be a good candidate for a high-density magnetic bubble-based memory

Summary

Introduction

Magnetic bubbles are small magnetized cylindrical volumes in magnetic films with uniaxial, perpendicular magnetocrystalline anisotropy that can be used for computer data storage [1]. The focus was on oxides that include rare-earth iron garnets, orthoferrites, and hexaferrites [2]. These materials exhibit magnetic bubbles with typical diameters in the 1–100 μm range. Owing to the large size, bubble memory cannot compete with semiconductor memories with a bit size of ∼30 nm. The need for smaller bubbles for commercial applications led to the recent introduction of the concept of skyrmions [3,4]

Results

Discussion

Conclusion