Reentrant Spin Glass and Magnetic Skyrmions in the Co7Zn7Mn6−xFex β-Mn-Type Alloys

Co7Zn7Mn6 is a β-Mn-type alloy belonging to the CoxZnyMnz (x+y+z=20) family that notoriously features a skyrmionic magnetic phase below the ferromagnetic ordering temperature and, in addition, a reentrant spin glass transition at low temperatures. In this work, we have studied the effect of partial substitution of Mn by Fe in the magnetic properties of this alloy. Samples of Co7Zn7Mn6−xFex, 0≤x≤1, were synthesised using the Bridgman–Stockbarger method, and their structure and composition were fully characterised by XRD and EDS. VSM and AC susceptibility measurements show that the partial substitution of Mn by Fe increases TC and the skyrmionic region of the magnetic phase diagram is suppressed for x>0.5. The AC susceptibility behaviour at low temperatures can be ascribed to the presence of a reentrant spin glass state observed for all compositions, with a spin glass freezing temperature, Tg, that shifts to lower temperatures as the Fe content increases.