Fig. 1

Alternating distribution of Nd and Ag columns in a \(\left( {{{10}}\bar {{1}}2} \right)\) twin boundary. a Atomic-resolution \(\left[ {\bar {{1}}2\bar {{1}}0} \right]\) HAADF-STEM image. b Enlargement of a region in a. c–e Corresponding atomic-resolution EDS maps showing atomic columns rich in c Nd, d Ag and e (Nd + Ag). Dashed circles in (b–e) indicate extension sites. f Atomic-resolution \(\left[ {\bar {{1}}{{011}}} \right]\) HAADF-STEM image. g Enlarged image of a boundary segment in (f). h–j Corresponding atomic-resolution EDS maps showing atomic columns rich in h Nd, i Ag and j (Nd + Ag). k Schematic diagram showing arrangement of Nd and Ag atoms within a \(\left( {{{10}}\bar {{1}}2} \right)\) twin boundary. Blue and red arrows indicate \(\left[ {\bar {{1}}2\bar {{1}}0} \right]\) and \(\left[ {\bar {{1}}{{011}}} \right]\) directions, respectively. l, m Segregation layer viewed along l \(\left[ {\bar {{1}}2\bar {{1}}0} \right]\) and m \(\left[ {\bar {{1}}{{011}}} \right]\). n, o Simulated \(\left[ {\bar {{1}}2\bar {{1}}0} \right]\) and \(\left[ {\bar {{1}}{{011}}} \right]\) HAADF-STEM images, respectively. Insets in (n) and (o) are experimental images