摘要
采用电子束反应蒸发生长Zn0.66Co0.34O薄膜,生长温度仅为250℃,尔后在Ar气氛中500℃退火1h。场发射扫描电镜测量显示薄膜由粒径约10～20nm的晶粒所构成。X射线衍射测量表明薄膜在退火前后均呈类ZnO的六方纤锌矿结构。振动样品磁场计测量室温下薄膜的M-H曲线,结果显示退火前薄膜呈超顺磁性,退火后则为铁磁、超顺磁混合态,这表明退火提供了足够能量使得薄膜中一部分磁性Zn0.66Co0.34O小晶粒融合成大晶粒,新晶粒的尺寸超过了Zn0.66Co0.34O材料的超顺磁临界半径而表现出铁磁性,但由于另有部分晶粒仍表现为超顺磁性,故薄膜呈铁磁性与超顺磁性的混合态。
Zn0.66Co0.34O films were grown by reactive e-beam evaporation at 250℃ and then annealed in Ar ambient at 500℃ for 1h.Scanning electron microscope,X-ray diffraction（XRD） and vibrating sample magnetometer（VSM） were employed to characterize the microstructure and magnetic properties of Zn0.66Co0.34O film.XRD measurements revealed that both of as-grown and annealed Zn0.66Co0.34O films are homogeneous with a pure wurtzite structure.Room temperature M-H curves tested by VSM show that the as-grown film is superparamagnetic while the annealed film demonstrates a mixed magnetic characteristics of ferromagnetism and superparamagnetism.Such results suggest that by annealing treatment,some small crystal grains coalesced into relatively larger crystallites,whose sizes exceeded the superparamagnetic critical radius of Zn0.66Co0.34O material and correspondingly showed their ferromagnetic nature.However,probably duo to the fact that other grains still kept superparamagnetic,so the film emerged a mixed magnetic state of superparamagnetism and ferromagnetism.
出处
《功能材料》
EI
CAS
CSCD
北大核心
2007年第7期1089-1092,共4页
Journal of Functional Materials
基金
国家自然科学基金资助项目(50472058)
