Fig. 1: Characterization of the FeCoNiCuPdIrPtAu nanoparticles and the “smaller-is-stronger” phenomenon in particles with diameter larger than 180 nm.

a HADDF image showing the morphology of a particle with diameters of 50 nm. b HADDF-STEM image showing the atomic structure of a particle containing a twin (beam direction [110]). c EDS mapping results showing how the eight elements are distributed in the particles. Cu, Au, and Pd display a similar distribution that is complementary to that of Fe, Co, Ni and Pt; note that there is no significant segregation of noble elements at the surface of the nanoparticles, and compositional variations occur within the nanoparticles (also see Supplementary Fig. 1) d, f Deformation of large particles with a diameter of 200 nm and 180 nm, respectively (frames are taken from Supplementary Movie 1 and 2); the centers of the particles were barely electron transparent due to their comparatively large size and because their composition comprised certain noble elements with large atomic numbers. e Engineering stress vs. contraction-in-height curves showing the “smaller-is-stronger” trend, based on tests on the particles in (d, f) and a larger 260 nm sized particle. The engineering stress was calculated from the continuously recorded load values and diameters calculated with the cylinder model (see Methods for details)). g True stress vs. expansion-in-maximum width diagrams of (d, f) (stresses were calculated from the real-time load values and diameters measured from the extracted frames).