Zigzag domain boundaries in magnetostrictive Fe-Ga alloys

A recent development in magnetic materials research on a non-Joulian magnetostriction phenomenon [H. D. Chopra and M. Wuttig, Nature 521, 340 (2015)] highlights peculiar cellular magnetic domains with zigzag boundaries in Fe-Ga alloys. The cause of zigzag boundaries of cellular domains is attributed to hypothetical charge density waves beyond classical magnetic domain theory. In this paper, we report observations in Fe-Ga alloys of zigzag boundaries that form conventional stripe domains. The responses of stripe domains to external magnetic fields are observed, and the behaviors of zigzag boundaries are examined, which are further compared with those in cellular domains. It shows that both cellular and stripe domains and the constituent zigzag boundaries in magnetostrictive Fe-Ga alloys can be explained well by classical magnetic domain theory, without resorting to theory based on hypothetical charge density waves. In particular, our findings provide convincing evidence that zigzag boundaries in Fe-Ga alloys are conventional V lines commonly observed in cubic magnetic crystals like Fe-Si alloys. The intricate cellular domain structure is shown to correlate with the simple stripe domain structure in terms of zigzag V lines and flux-closure surface domains.