Co-C-2 nanocluster magnets are formed in amorphous carbon by high pressure reaction Of Co-4(CO)(12) and CH2Cl2. 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 (CoC2)(n) with pi 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. (C) 2003 Elsevier Science B.V. All rights reserved.