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.