Determination of domain wall energy and critical single-domain particle size based on domain structure observations of ThMn12-type magnetic particles

•Domain width and grain size of selected ThMn12 structure compounds were measured.•Well characterized Sm2Fe17N3 particles were used as standard for measurements.•Domain wall energy (γ) and single-domain grain critical size (Rc) were calculated.•Classical equations for domain structure analyses were used for the calculations.•The determined γ, Rc, exchange stiffness A, exchange integral Jij were listed. The domain structures of standard Sm2Fe17N3 particles and three almost α-(Fe,Co)-free magnetic compounds with a ThMn12-type structure, namely, (Sm0.9Zr0.1)(Fe0.8Co0.2)11.3Ti0.7, (Nd0.8Zr0.2)(Fe0.9Co0.1)11.3Ti0.7N1.5, and Nd(Fe0.8Co0.2)11MoN1.3, were examined via magnetic force microscopy. Using the observed domain widths (d) and particle sizes (D) in conjunction with classical equations, the domain wall energy (γ), critical single-domain particle size (Rc), exchange stiffness (Aex), and exchange integral (Jij) of the compounds were calculated.