Heterostructured Co-Au nanoparticles are direct synthesized from gas phase. Magnetic properties of Co-Au nanoparticles are characterized. Low-temperature and room-temperature hysteresis loops show that the magnetic properties of Co are kept in Co-Au nanoparticles. A blocking temperature of 290 K is measured for Co-Au particles with an average size of 12 nm. A field-cooled low-temperature hysteresis loop of Co-Au nanoparticles indicates the existence of oxide, even the particles have a core-shell-like structure.
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The authors would like to thank Dr. S. McKernan and Dr. J. Basu for TEM and composition analysis, Dr. J. Thomas for XPS analysis, Prof. C. Leighton for SQUID usage, and Dr. J. M. Bai and J.-M. Qiu for fruitful discussion. This work was supported in part by Seagate Technology and Heraeus Corporation. The integrated nanoparticle deposition system used in this paper was set up through one of the authors JPW’s_faculty startup fund from the University of Minnesota.