  Control of emergent magnetic orders in correlated electron materials promises
new opportunities for applications in spintronics. For their technological
exploitation, it is important to understand the role of surfaces and interfaces
to other materials and their impact on the emergent magnetic orders. Here, we
demonstrate for iron telluride, the nonsuperconducting parent compound of the
iron chalcogenide superconductors, determination and manipulation of the
surface magnetic structure by low-temperature spin-polarized scanning tunneling
microscopy. Iron telluride exhibits a complex structural and magnetic phase
diagram as a function of interstitial iron concentration. Several theories have
been put forward to explain the different magnetic orders observed in the phase
diagram, which ascribe a dominant role either to interactions mediated by
itinerant electrons or to local moment interactions. Through the controlled
removal of surface excess iron, we can separate the influence of the excess
iron from that of the change in the lattice structure.
