EXPERIMENTAL-STUDY OF FERROMAGNETIC CHAINS COMPOSED OF NANOSIZE FE SPHERES

Chains composed;of nanometer size spheres of Fe have been synthesized by a controlled reduction at ambient temperature of aqeous-Fe2+ with K BH4 in the presence of an applied magnetic field The chains are charac terized by x-ray diffraction, transmission electron microscopy, and su perconducting quantum interfer ence device magnetometry. The size of t he crystalline Fe spheres could be varied from 20 to 70 nm by controll ing the synthesis conditions. The magnetization reversal behavior of t hese chains are examined and compared with the theoretical predictions of the ''chain of spheres model.'' The observed values of the coerciv e force H-c, variation of H-c with particle size, relationship between the H-c values of randomly oriented and aligned chains, remanence of randomly oriented chains, and angular dependence of H-c in the single- domain region are all in support of a symmetric fanning mechanism for magnetization reversal. This study represents an example of fabricatio n of a true chain of spheres and comparison of their magnetic properti es with theoretical predictions available in the literature.