Ferromagnetism at room temperature mediated by defects in Co doped and undoped Cu2O layers

IURI S. BRANDT; MILTON A. TUMELERO; E. LIMA JR.; R.D. ZYSLER; ANDRE A. PASA

Rio de Janeiro

Congreso; XIV Brazil MRS Meeting ? Rio 2015; 2015

MRS Brasil

Dilutedmagnetic semiconductors (DMSs) have been considered for potential applicationin spintronic devices1. Doped oxide-based semiconductors have shownto be good candidates as DMS materials with Curie temperatures above RT2.However, ferromagnetism (FM) has also been observed in undoped oxides. Theorigin of the FM in doped and undoped oxides is still unclear and under subjectof intense investigation due its technological relevance. This work presents afull characterization of Co doped and undoped Cu2O thin filmsobtained by electrodeposition technique. Important results are obtained, asdoped films with ferromagnetic behavior at least up to 700 K. Surprisinglyundoped films also presented ferromagnetism at room temperature, which couldindicated that the observed magnetic behavior is mediated by defects, e.g.copper vacancy or interstitial oxygen. The sample magnetization was reduced asa consequence of defect density decreasing by annealing. Polarization-dependentX-ray absorption measurements demonstrated that the observed magnetic momentarises from Co and O2pCu hybridized states. Structural, optical andelectrical characterization provides information that confirms theincorporation of Co atoms in the Cu2O lattice, without the formationof secondary phases. In addition, Electron Paramagnetic Resonance and GlowDischarge Optical Emission Spectroscopy measurements reject the existence ofcontaminants in the films, dismissing it as the responsible for the observedmagnetism. We have performed DFT calculations to find out the role played bythe Co atoms and the origin of the magnetic moments in our samples. Suchsimulations showed the need for copper vacancy or interstitial oxygen living inthe Cu2O lattice to the observation of a net magnetic moment.