Magnetism of antiphase boundaries in ordered alloys studied using electron holography

•Electron holography demonstrates magnetic anomalies in antiphase boundaries (APBs).•In many alloys, ferromagnetism is depressed by structural disorder in APBs.•In Fe70A130 alloy, ferromagnetism can be developed by APBs.•The observations provide useful information for engineering APB-induced phenomena. Magnetic anomalies in antiphase boundaries (APBs), which are a type of planar defect produced in ordered crystals, have been studied using electron holography. For many ordered crystals, including a Ni50Mn25Al12.5Ga12.5 alloy with a Heusler-type structure, atomic disordering in the APB region (showing a finite thickness) deteriorates the ferromagnetic spin order. This relationship has several functions, such as the pinning of magnetic domain walls by APBs. However, in an Fe70A130 alloy with a B2-type (CsCl-type) ordered structure, ferromagnetism can be developed by APBs. The unusual relationship observed in the Fe70A130 alloy can provide useful information for engineering APB-induced phenomena. This paper reviews recent electron holography observations from these two types of alloys, and technical advancements in the APB studies.