Magnetic Reconstruction at Grain Boundaries in Ni-dihalides

Area of Science:

• Condensed Matter Physics
• Materials Science
• Magnetism

Background:

• Grain boundaries (GBs) significantly influence polycrystal properties.
• Atomic reconstruction and magnetism at GBs in van der Waals (vdW) magnets are understudied.

Purpose of the Study:

• To systematically investigate thermodynamically stable GBs in magnetically frustrated Ni-dihalides.
• To understand the atomic reconstruction and resulting magnetic properties at these GBs.

Main Methods:

• First-principles calculations to model atomic configurations and magnetic interactions at GBs.
• Analysis of magnetic moments, coupling, and domain structures.
• Investigation of skyrmion/antiskyrmion nucleation, stability, and dynamics.

Main Results:

• Reconstructed GBs suppress local magnetic moments but induce antiferromagnetic coupling between four-coordinate Ni atoms.
• Formation of segmented helical magnetic domains aligned antiferromagnetically.
• Stabilization of ultrasmall metastable skyrmions/antiskyrmions (∼1.4 nm) pinned at GBs, stable up to 18 T.
• Nucleation and motion of nanometer-sized skyrmions/antiskyrmions along GBs under spin-transfer-torque.

Conclusions:

• GBs in vdW magnets exhibit unique reconstructed atomic configurations with distinct magnetic properties.
• These findings offer a novel strategy for stabilizing and controlling skyrmions, potentially eliminating the skyrmion Hall effect.