Magnetization reversal induced by antiphase domain boundaries in Ni2MnZ Heusler compounds

The correlation of the microstructure and the magnetic properties of ${\mathrm{Ni}}_{\text{2}}{\mathrm{MnAl}}_{\text{0.5}}{\mathrm{Ga}}_{\text{0.5}}$ and ${\mathrm{Ni}}_{\text{2}}\mathrm{MnAl}$ Heusler alloys is studied in samples of distinct $\mathrm{L}{2}_{\text{1}}$ order states by neutron powder diffraction and small-angle scattering. The extracted correlation lengths of the structural and magnetic order agree over all annealing states, which implies the structural antiphase domain boundaries to be identical to the magnetic domain walls, and thus to inherently give rise to a magnetization reversal. The findings are discussed in the context of recent small-angle neutron scattering studies on related systems, and their wider implications are pointed out.