High-field magnetization process in free radical and metal-assembled molecular magnets

We applied the high-field technique to study the magnetization process in m odel substances. Measurements have been performed on the powder samples und er a pulsed magnetic field up to 50 T, A family of organic verdazyl radical is a candidate of an isotropic S = 1/2 antiferromagnetic linear chain mode l, The observed magnetization is practically zero up to a certain critical field around 40 T and steeply increases to the saturation value of 1 mu(B)/ molecule. The feature cannot be explained by the uniform chain model but ag rees with the alternation linear chain model closed to the dimer model in w hich the ground state is a nonmagnetic singlet with an energy gap between t he excited triplet state. Metal-assembled tetranuclear complexes [Mn(MeOH)L (OH)M(bpy)](2) represent a prototype of geometrically frustrated spin syste ms. We observed a step-like magnetization process which clearly shows the s uccessive transitions among quantum states with different total spins.