【摘要】 用电子束反应蒸镀法在低温生长了Zn1-xCoxO薄膜．Co含量x高达0．33的Zn1-xCoxO薄膜仍具有类ZnO的纤锌矿结构,没有杂质相,Co的化合价为+2．场冷和零场冷M-T及M-H曲线表明,Zn1-xCoxO(x=0．33)薄膜在低温下具有铁磁性;随着温度的升高,其剩磁和矫顽力均逐渐下降,在65 K以上趋于零,显示出超顺磁性．Zn1-xCoxO薄膜的低温铁磁性起源于Co2+离子之间的双交换相互作用及载流子诱导的sp-d交换耦合作用,而从低温(<65 K)铁磁态到高温(>65 K)超顺磁态的转变可归因于薄膜的纳米晶小尺寸效应．更多还原

【Abstract】 Zn1-xCoxO films were grown by reactive electron beam evaporation at low temperature. X-ray diffraction measurements revealed that homogeneous alloy films of Zn1-xCoxO are realized without impurity phases segregated up to x=0.33. X-ray photoelectron spectra analysis indicated that the valence of Co in the film is+2. Combined magnetic investigations of M-H and M-T curves for field-cooled and zero-field-cooled conditions showed that Zn1-xCoxO (x=0.33) films are ferromagnetic below 65 K. While above 65 K, hysteresis and remanence disappeared and superparamagnetism is shown. Low-temperature ferromagnetism of Zn1-xCoxO film is originated from Co2+-Co2+ double-exchange interactions and/or the exchange interactions between sp-band electrons of ZnO and localized 3d electrons around Co2+ ions. The transition from ferromagnetism to superparamagnetism is due to the small size effect of nanoparticles in the films.更多还原