New paramagnetic defects in synthetic diamonds grown using nickel catalyst

We report four new EPR spectra found in high-pressure synthetic diamonds wi th high nitrogen content, grown using nickel, and annealed at 1600 degrees C. Analyzing the complex spectra around g approximate to 2 two trigonal and two orthorhombic defects, all with S = 1/2, were identified from the angul ar dependence and the different saturation behavior of the transitions. Bes ides optical and EPR investigations reveal several centers which have been previously ascribed to defects containing nickel and nitrogen. However, nit rogen is not involved in the new centers, since no evidence of an N-14 hype rfine structure could be found. Possible relations of the new defects with Ni are discussed. (C) 1999 Elsevier Science B.V. All rights reserved.