In-situ lorentz and electron-holography imaging of domain-wall propagation and grain-boundary pinning within anisotropic Nd-Fe-B sintered-magnet thin films

•In-situ Lorentz imaging of magnetization reversal from saturated state in Nd-Fe-B magnets.•Propagation of head-on domain walls (DWs) parallel to the easy axis.•DW pinning at c-plane grain boundaries (GBs) and its local magnetization configuration.•Propagation of long DW across several GBs perpendicularly to the easy axis.•Zig-zag composite DWs pinned at c-plane GBs reducing magnetostatic energy.