COMPLETE SET OF MAGNETIC PARAMETERS IN A NOVEL NICKEL(II) CHELATE

A theoretical analysis of powder magnetic data based on the diagonaliz ation of the spin Hamiltonian matrices is outlined. The first and seco nd 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-mem ber Ni(II) metallocycle (S=1) was investigated by SQUID measurements d own to 2K and a substantial drop of the chi T curve below 25K was foun d. A reconstruction of the components of the magnetic susceptibility w as done. An independent fitting procedure using four fundamental magne tic 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 t hat a selfconsistency of magnetic parameters is proven. (C) 1998 Elsev ier Science B.V.