High-field magnetization of an S=1/2 F-F-AF-AF tetramer chain

We performed magnetic susceptibility and high-held magnetization measuremen ts on a powder sample of a copper tetramer chain compound Cu(3-Clpy)(2)(N-3 )(2) (3-Clpy = 3-Chloropyridine). Magnetic susceptibility (chi) times tempe rature (T) decreases gradually with decreasing temperature from 300 K and i ncreases steeply after reaching a minimum at 10 K. The high-field magnetiza tion of this compound at 1.3 K shows a plateau at a half of the saturation magnetization up to 250 kOe and a successive abrupt increase near the satur ation field. We compare these experimental data with those calculated for t he S = 1/2 ferromagnetic-ferromagnetic-antiferromagnetic (F-F-AF-AF) tetram er chain and obtained fairly good agreement between them when the ratio of the ferromagnetic exchange constant to the antiferromagnetic one is - 0.5. The abrupt increase of magnetization near the saturation field is discussed . (C) 2001 Elsevier Science B.V. All rights reserved.