Magnetic properties of one-dimensional compounds An+2COn+1O3n+3 (A = Ca, Sr, Ba; n=1-5)

We have investigated the magnetic properties of one-dimensional (1D) compounds A(n+2)Co(n+1)O(3n+3) (A = Ca, Sr, Ba) by susceptibility measurements. The transition to a partially disordered antiferromagnetic state, which takes place at 25 K for Ca3Co2O6 (n = 1), was not observed down to 2 K for the n = 2-5 samples, except that a precursory behavior was found for n = 2 below 3.2 K. The absence of a long-range order in the n = 2-5 samples can be understood by accounting for the increase in the distance between the 1D CoO3 chains, which are characteristic to the present compounds. At high temperatures, we observed a change in the slope of the temperature dependence of the inverse susceptibility, which we attribute to the appearance of a short-range 1D ferromagnetic order along the CoO3 chain. (c) 2006 Elsevier B.V. All rights reserved.