Isolated Fe-Co-Ni nanoparticles in a random arrangement and their magnetic properties

Fe-Co-Ni particles with an average size of 45 and 135 nm are characterized in terms of magnetic phase transformation and magnetic properties at room temperature. The bcc structure of Fe-Co-Ni spherical particles was able to be synthesized from Fe-Co-Ni-Al-Cu precursor films by heating at 600-800 degreesC for the phase separation of Fe-Co rich Fe-Co-Ni particles, followed by a postheating at 600 degreesC for 5 h. The average size of nanoparticles was directly determined by the thickness of precursor films. Exchange interactive hysteresis was observed for the nano-composite (Fe-Co-Ni)+(Fe-Ni-Al) films resulting from the short exchange interface between ferromagnetic Fe-Co-Ni particles surrounded by an almost papramagnetic Ni-Al-Fe matrix. Arraying the isolated Fe-Co-Ni nanoparticles in a random arrangement on Al2O3 substrate, the particle assembly showed a behavior of dipole interactive ferromagnetic clusters depending on their volume and interparticle distance. (C) 2001 American Institute of Physics.