Two types of magnetic bubbles in MnNiGa observed via Lorentz microscopy

TL;DR

This study uses Lorentz microscopy to reveal two distinct types of magnetic bubbles in MnNiGa, clarifying previous contradictory reports and linking bubble types to the orientation of the magnetic easy axis.

Contribution

It demonstrates the dependence of magnetic bubble type on the easy axis orientation in MnNiGa, resolving prior conflicting observations.

Findings

Two types of magnetic bubbles observed depending on easy axis orientation

Contrast of biskyrmions reproduced by magnetic bubble form

Fills knowledge gap on magnetic bubble structures in MnNiGa

Abstract

Magnetic bubbles are remarkable spin structures that developed in uniaxial magnets with strong magnetocrystalline anisotropy. Several contradictory reports have been published concerning the magnetic bubble structure in a metallic magnet MnNiGa: Biskyrmions or type-II bubbles. Lorentz microscopy in polycrystalline MnNiGa was used to explain the magnetic bubble structure. Depending on the connection between the magnetic easy axis and the observation plane, two types of magnetic bubbles were formed. Magnetic bubbles with 180{\deg} domains were formed if the easy axis was away from the direction perpendicular to the observation plane. The contrast of biskyrmion is reproduced by this form of a magnetic bubble. When the easy axis was approximately perpendicular to the observing plane, type-II bubbles were observed in the same specimen. The findings will fill a knowledge gap between prior reports on magnetic bubbles in MnNiGa.