Magnetic Domain Fine Structures in (Fe,Cr)2B: Insights from Lorentz TEM, Local Composition, and Structural Characterization (12/10/26)
Speaker and Affliation:
Dr. Chanchal Ghosh
Physical Metallurgy Division, IGCAR, Kalpakkam
When?
12th October, 2026 (Monday), 11.00 AM (India Standard Time)
Where
KPA Auditorium, Department of Materials Engineering
Abstract:
In the present study, we demonstrate that chromium plays a crucial role in enabling the formation of magnetic textures (e.g., magnetic stripes, bubbles) at room temperature within the (Fe,Cr)2B phase in a boride-ferrite composite (BFC) system. In (Fe,Cr)2B structure, Cr substitutes at Fe lattice sites while preserving the original Fe2B crystal structure. The material comprises two distinct phases of (Fe,Cr)2B borides: an eutectic structure comprising finer particles and pro-eutectic (Fe,Cr)2B borides consisting larger faceted grains. Cr content in these borides was quantified to be approximately 8 wt.% in the finer borides and 11 wt.% in the coarse ones. Formation of magnetic texture and its stability under externally applied magnetic fields were examined using Lorentz Transmission Electron Microscopy (LTEM), leveraging the microscope’s objective lens for in situ field application.
Remarkably, circular and elliptical magnetic bubble were preferentially observed only within the finer borides, with lower Cr concentration (8 wt.%), whereas the large faceted borides (Cr conc. ~ 8 wt.%) show only the formation of magnetic stripes, indicating a strong compositional dependence. Their room-temperature stability arises from a delicate balance among the Dzyaloshinskii–Moriya interaction (DMI), exchange interactions, and magnetic anisotropy. Micromagnetic simulation has been performed to understand the role of these parameters in the formation of magnetic textures. The origin of these contrast has been investigated through the analysis of localized structure, chemistry and residual stress of the borides.