Complete set of magnetic parameters in a novel nickel(II) chelate

A theoretical analysis of powder magnetic data based on the diagonalization of the spin Hamiltonian matrices is outlined. The first and second derivatives of the eigenvalues are determined from the fourth-order polynomial fit; they enter the van Vleck formula for the paramagnetic susceptibility. The procedure is capable of subtracting the complete set of magnetic parameters from powder susceptibility data. A five-member Ni(II) metallocycle (S=1) was investigated by SQUID measurements down to 2K and a substantial drop of the chi T curve below 25K was found. A reconstruction of the components of the magnetic susceptibility was done. An independent fitting procedure using four fundamental magnetic parameters gave Lambda(xx) = 42.8 +/- 0.1, Lambda(yy) = 49.9 +/- 0.1, Lambda(zz) = 26.6 +/- 0.1 au and (z)J/hc = -2.06 +/- 0.01 cm(-1). These data reproduce the enlarged set of magnetic parameters well so that a selfconsistency of magnetic parameters is proven. (C) 1998 Elsevier Science B.V.