Fig. 1

Assembly and spin switching of the trimer–satellite atom complex. a Constant-current STM images (5 × 5 nm², the scale bars have a length of 1 nm, \(V = 5\,{\mathrm{mV}}\), \(I = 500\,{\mathrm{pA}}\)) of the construction process of a complex via lateral atom manipulation (\(V_{{\mathrm{manip}}} = 1.1\,{\mathrm{mV}}\), \(I_{{\mathrm{manip}}} = 25\,{\mathrm{nA}}\)). A single iron atom is approached to the trimer. Within the complex the atom sits on an fcc adsorption side labeled as a in Fig. 2a. In this complex, the distance between atom and trimer is d = 0.97 nm. b Time traces of the apparent height recorded on the trimer (black, upper panel) and on the atom (red, lower panel) (V = 2.75 mV, I = 200 pA, B = 0 T, T = 300 mK). The data sets are shifted vertically for better visibility. c Illustration of the contrast mechanism for the data taken on the fast switching atom ferromagnetically coupled to a trimer in an SP-STM measurement. The fast switching events are averaged out during the measuring time, leading to a change in the apparent height of the atom when the trimer switches as indicated by the dark red lines. d Constant-current STM image of the complex recorded with an out-of-plane spin-polarized tip (the scale bar has a length of 1 nm, V = 3 mV, I = 50 pA, B = 0 T, T = 300 mK). e Consecutively recorded spin-resolved line scans along the dashed line in (d) stacked on top of each other (V = 3 mV, I = 20 pA, B = 0 T, T = 300 mK, scanning time per line = 614 ms)