EPR characterization of Co-doped ZnO microwires and distant spin-pair coupling

International audienceCobalt-doped ZnO microwires have been grown by the optical furnace method with Co concentration in the range 0-5%. The high crystallinity of these objects is demonstrated by the use of electron paramagnetic resonance (EPR), in which Co 2+ ions serve as magnetic probes. The spin state of these isolated magnetic impurities and their location in the host crystal are addressed by EPR, as well as the coupling constant between non-nearest Co 2+-Co 2+ neighbors. Eight of these distant spin pairs are detected, among which two are confirmed to be ferromagnetic. The problem of their localization in the wurtzite structure is discussed