Long-range magnetic ordering in the spin-chain compound Ca₃CuMnO₆ with multiple bond distances

Abstract

The results of ac and dc magnetization and heat-capacity measurements as a function of temperature (T=1.8-300K) are reported for a quasi-one-dimensional compound, Ca₃CuMnO₆, crystallizing in a triclinically distorted K₄CdCl₆-type structure. The results reveal that this compound undergoes antiferromagnetic ordering close to 5.5 K. In addition, there is an additional magnetic transition below 3.6 K. The existence of two long-range magnetic transitions is uncommon among quasi-one-dimensional systems. It is interesting to note that both the magnetic transitions are of long-range type, instead of spin-glass type, in spite of the fact that the Cu-O and Mn-O bond distances are multiplied due to this crystallographic distortion. In view of this, this compound could serve as a nice example for studying "order-in-disorder" phenomena.