Absence of room-temperature ferromagnetism in Al-codoped Zn0.95Co0.05O nanoparticles

Abstract Nanocrystalline Zn 0.95− x Co 0.05 Al x O ( x = 0, 0.01, 0.05) diluted magnetic semiconductors have been synthesized by an auto-combustion method. X-ray diffraction measurements indicated that Al-doped Zn 0.95 Co 0.05 O samples had the pure wurtzite structure. X-ray absorption spectroscopy, high-resolution transmission electron microscope, energy dispersive spectrometer and Co 2 p core-level photoemission spectroscope analyses indicated that Co 2+ substituted for Zn 2+ without forming any secondary phases or impurities. Resistance measurements showed that the resistance values of Co and Al codoped samples were still so large in the giga magnitude. Magnetic investigations showed that nanocrystalline Al-doped Zn 0.95 Co 0.05 O samples had no indication of room temperature ferromagnetism.