Atomic‐Scale Magnetic Properties of Truly 3d‐Diluted ZnO

In search for dilute magnetic semiconductors, the magnetic properties at the atomic‐scale of Fe atoms incorporated in ZnO, in a concentration range of more than five orders of magnitude from 1 × 10−5 to 2.2 at% have been probed using emission 57Fe Mössbauer spectroscopy on implanted 57Mn and 57Co produced at ISOLDE/CERN. In the ultra‐dilute regime (10−5 at%), the system shows isolated paramagnetic Fe3+ ions with a spin–lattice type of relaxation. At higher concentrations (between 0.02 and 0.2 at%) a transition to spin–spin type of relaxation between neighboring Fe3+ is observed, without any signature of magnetic ordering up to 2.2 at%. Despite the many reports of dilute magnetism in 3d‐doped ZnO, this atomic level study shows no evidence of any long‐range magnetic ordering between isolated Fe atoms incorporated in the ZnO lattice. Long‐range magnetic interactions, as have been proposed to occur in transition metal‐doped and undoped ZnO systems in recent years, are not found on an atomic‐scale. This is demonstrated by performing on‐line Mössbauer spectroscopy in ZnO at ISOLDE/CERN, in a 3d‐atoms concentration range of more than five orders of magnitude from 1 × 10−5 to 2.2 at%.