Fe-Cu和Fe-Ag金属颗粒膜的磁性  

MAGNETIC PROPERTIES OF GRANULAR Fe-Cu AND Fe-Ag ALLOYS

作　　者：彭初兵[1] 张胜[1] 刘尊孝[1] 胡永建 李国忠[1] 戴道生[1] 

机构地区：[1]北京大学物理系,北京100871

出　　处：《物理学报》1995年第4期653-659,共7页Acta Physica Sinica

基　　金：国家自然科学基金;中国科学院物理研究所磁学国家重点实验室资助的课题

摘　　要：报道了Fe-Cu和Fe-Ag金属颗粒膜的晶体结构和磁性。电子衍射和高分辨透射电子衍射分析证实:在这些样品中铁颗粒从cu或Ag中脱溶出来而均匀分布在整个样品中。磁测量表明,当样品中铁成分较低时(x<0.25),在较高温度下,存在铁磁-超顺磁相变。基于超顺磁性理论,可以很好地解释铁颗粒有效磁矩随外磁场的变化特性,并且由此估计了铁磁颗粒的平均大小。在1.5K温度下,当样品中铁成分较低时(x<0.20),铁颗粒平均原于磁矩低于大块材料。在低温下,磁化强度对温度的依赖性测量表明,随着样品中铁成分的降低,样品磁性呈现从三维向二维转变。铁磁共振测量间接地证实了这种磁性特性。We have studied the structure and magnetic properties of metallic granular FexCu1-x (x=0-0.35) and FexAg1x(x=0-0.45) alloys. These alloy films were fabricated by using a coevaporation method under a vacuum of 10-5 Pa onto liquid-nitrogen cooled substrates. Electron diffraction and high resolution electron microscope obser-vations confirmed that these films consists of small iron particles embedded in Cu (Ag) matrix. The ferromagnetic-superparamagnetic transition occurs above blocking temperature. The blocking temperature, dependent on the iron granular sizes, is in a range of 60 to 300 K as x= 0.08-0.22. Above the blocking temperature, samples exhibit superparamagnetic relaxation; Their magnetic behavior can be explained based on superparamagnetic theory. From the fitting, the average iron particle size is estimated to be in the range of 1 to 4nm. At 1.5 K, the average magnetic moment of iron atoms is reduced as the average number of iron atoms in a particle is less than 450. At low temperature, the temperature dependence of magnetization has re-vealed that the magnetic properties of iroo particles evolve from three- to two-dimen-sional magnetism as iron concentration is reduced.

关 键 词：颗粒膜 铁-铜 铁-金 磁性 金属颗粒膜 

分 类 号：O484.43[理学—固体物理]