Nature of magnetism in the spin-chain compound, Ca3CuRuO6

A quasi one-dimensional compound, Ca3CuRuO6, has been synthesized by solid-state reaction method and studied using magnetization (M) and heat capacity (C) measurements. This compound undergoes magnetic ordering (T_o) around 40 K, as evidenced by the dc magnetic susceptibility (chi) behavior. However, the magnitude of the paramagnetic Curie temperature (theta_p) obtained from the high temperature linear region is large (-277 K, with the negative sign indicating antiferromagnetic interaction). The reduction of T_o, compared to theta_p, is attributed to geometrical frustration effect arising from the triangular arrangement of antiferromagnetically coupled magnetic chains. The absence of a feature in ac chi around 40 K rules out possible spin-glass freezing. However, we find that the peak in C(T) around 40 K is weak, with the entropy change associated with the transition being negligible, typical of a disordered magnetism. We infer that this material thus exhibits inhomogeneous magnetism, despite being stoichiometric, presumably due to an interplay between disorder in the Cu-Ru chain.

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