Multi-instrumental approach to domain walls and their movement in ferromagnetic steels – Origin of Barkhausen noise studied by microscopy techniques

•Hypotheses related to the origin of Barkhausen noise signal are visualized and verified by multi-instrumental microscopy techniques.•Thorough characterization of plain ferrite, containing several features theoretically affecting BN output, enabled resolving origin of varying BN signal levels.•Multi-instrumental characterization of complex ferrite-pearlite elaborated interaction of domain walls and pinning sites, i.e., origin of BN.•Bulk and thin samples have a similar domain structure, but different BN signals due to contribution of thin sample’s both surfaces.•In-plane domain wall movement under out-of-plane applied magnetic field is explained using anisotropy energetics.