Magnetic Properties Of Co Doped ZnO Based Diluted Magnetic Semiconductors

Diluted magnetic semiconductor materials could combine the charge degree of freedom and spin degree of freedom in single material to process information.It has broad application prospects in high-density storage,semiconductor integrated circuits,semiconductor lasers and quantum computers etc,and have attracted more and more attention.However,the mechanism of ferromagnetism is still controversial.Therefore,to find the mechanism of ferromagnetism of dilute magnetic semiconductors,a large number of relevant theoretical and experimental research are still necessary.In this paper,the magnetic properties of Co doped ZnO were studied by injecting Al ions by ion implantation and applying magnetic field when the samples were prepared by hydrothermal method and sol-gel method.The main contents and conclusions of this paper are as follows:?1?Co doped ZnO bulk samples were prepared by traditional solid state reaction method under four different sintering temperature,and then Al ions were implanted.XRD showed that all the samples had no second phase.After the injection of Al³⁺,the crystallinity of the sample became slightly worse,and the optimum sintering temperature was 1200?.The Hall effect test showed that the injection of Al³⁺could lead to the huge increase of carrier concentration.The M-H curve showed that all the samples have room temperature ferromagnetism,and the magnetic properties didn't change too much after the injection of Al³⁺.The great changes in electrical properties and no obvious changes in magnetic properties of Co-Al codoped ZnO suggested that the ferromagnetism of the sample was not mediated by the carrier.The Raman analysis revealed that the room temperature ferromagnetism was related to the oxygen vacancy.?2?Co doped ZnO powder samples were prepared by magnetic field assisted hydrothermal method.The effects of the time of imposition of the magnetic field and different doping concentrations with the same magnetic field conditions on magnetic properties of samples were studied.The results showed that when magnetic field was applied more than 2 hours,the saturation magnetization increased by nearly three times.The same magnetic field conditions brought different effects on the samples with different doping concentration.The samples with the concentration of 3%had the strongest magnetic properties and showed the most conspicuous change.Raman and PL spectra showed that the ferromagnetism of the sample was caused by the ferromagnetic exchange mediated by the singly ionized oxygen vacancy.?3?The powder samples of Co doped ZnO were prepared by magnetic field assisted sol-gel method,and the effect of magnetic field on the magnetic properties of the samples was studied.SEM showed that the shape of particles were regular six prism,and the top and bottom surfaces were honeycomb like.The surfaces of six prism were densely attached to nano scale irregular particles.XRD and EDS showed that irregular particles may be Co₃O₄.VSM showed that the imposition of the magnetic field could improve the magnetic properties of the sample.