Magnetic properties of one-dimensional Heisenberg chains with ferromagnetic-antiferromagnetic bond alternation

We report the results of susceptibility and magnetization measurements on ferromagnetic-antiferromagnetic alternating chain compounds [Cu(TIM)]CuCl4 (TIM=2,3,9,10-tetramethyl-1,3,8, 10-tetraenecyclo-1,4,8,11-tetraazatetradecane) and (4-BzpipdH)CuCl3 (4-BzpipdH-4-benzylpiperidinium). Magnetization curves of both compounds are compared to those calculated for an S=1 linear-chain Heisenberg antiferromagnet. From the fitting of susceptibility data to a numerical formula calculated for an S=1/2 ferromagnetic-antiferromagnetic alternating chain [Inog. Chem. 33 (1994) 5171], we have estimated the antiferromagnetic exchange constant J(AF)/k(B)=2.9 K, the ferromagnetic exchange constant \J(F)\/k(B)=4.7 K and the g-value of the magnetic moment g=2.06 for the former and J(AF)/k(B)=8.8 K, \J(F)\/k(B)=38.8 K and g=2.17 for the latter, which are different from the values reported previously.