Sérgio Magalhães

Magnetism in Ar-implanted ZnO

ZnO single crystals were implanted with Ar ions with an energy of 100 keV and different fluences. Ferromagnetic behaviour is observed at room temperature after implantation. This behaviour is suppressed after consecutive annealings at 400 and 500 °C. Although trace transition metal impurities have been identified in the virgin samples, it is shown that they cannot account for the observed magnetic behaviour that is assigned to the presence of implantation-induced lattice defects.

Strain and interface effects on the magnetic and transport properties of La0.7Ca0.3MnO3/CaO multilayers

La0.7Ca0.3MnO3/CaO (LCMO/CaO) multilayers were deposited on (100) LaAlO3 substrates by pulsed injection metal organic chemical vapour deposition. The samples were characterised by X-ray diffraction, transport and magnetization measurements. An anomalous behaviour of the electrical resistance under applied magnetic field and an exchange bias effect for the magnetization are observed for the multilayers with thinner LCMO layers. These results suggest the existence of a short range antiferromagnetic coupling at the layer interfaces.