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The antiphase boundaries (APBs) in Ni-Mn-Ga Heusler alloys with L21 ordering have been so far possible to observe only in the foils using electron holography. Here, we present the possibility to observe the APBs in bulk materials by conventional magnetic force microscopy using particularly oriented and magnetized single crystal samples in the martensite state. The bipolar APB contrast occurs where in-plane magnetization is oriented perpendicularly to APBs. This is in agreement with a qualitative model of an APB as a planar non-magnetic layer in the ferromagnetic matrix.
Description
Visualization of antiphase boundaries using atomic force microscopy - modeled expected contrast for perpendicular interfaces (left), experimental observation (right)