Formation and magnetic characteristics of cobalt–carbon nanocluster magnets embedded in amorphous carbon matrices

• Published in: Chemical physics letters Vol. 369; no. 1; pp. 198 - 203
• Main Authors: Nishi, Nobuyuki, Kosugi, Kentaroh, Hino, Kazuyuki, Yokoyama, Toshihiko, Okunishi, Eiji
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 07-02-2003; Elsevier Science
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Exact sciences and technology; Magnetic properties and materials; Magnetic properties of nanostructures; Physics; Magnetization; Ferromagnetic materials; Magnetic hysteresis; Cobalt compounds; Experimental study; Materials preparation; Nanoparticles; Solid clusters; EEL spectroscopy; Chemical preparation; Scanning transmission electron microscopy; Microstructure; Carbon compounds
• ISSN: 0009-2614; 1873-4448
• DOI: 10.1016/S0009-2614(02)02005-5

Co–C
2 nanocluster magnets are formed in amorphous carbon by high pressure reaction of Co
4(CO)
12 and CH
2Cl
2. The average size of the clusters is 12 nm. Structural characteristics are investigated by transmission electron microscope (TEM), electron energy loss spectroscopy (EELS), extended X-ray absorption fine structure (EXAFS) analyses, and infrared spectroscopy suggesting that the clusters are (CoC
2)
n
with π bonds in C
2
2−. The magnetization decreases with decreasing temperatures from room temperature to 20 K, while 10 Oe field-cooling (FC) results in increasing magnetization at lower temperatures.