Magnetic anomalies in nanocrystalline , a geometrically frustrated spin-chain compound

We have investigated the magnetic behavior of nano crystals, synthesized by high-energy ball-milling, for a well-known geometrically frustrated spin-chain system, Ca₃CoRhO₆, and compared its magnetic characteristics with those of the bulk form by measuring ac and dc magnetization. The features attributable to the onset of ‘partially disordered antiferromagnetism’ (characterizing the bulk form) are not seen in the magnetization data of the nano particles; the magnetic moment at high fields in the very low temperature range in the magnetically ordered state gets relatively enhanced in the nano particles. It appears that the ferromagnetic intrachain interaction, judged by the sign of the paramagnetic Curie temperature, is preserved in the nano particles. These trends are opposite to those seen in the nano particles of Ca₃Co₂O₆. However, the complex spin-dynamics as evidenced by large frequency dependence of ac susceptibility is retained in the nano particles as well. Thus, there are some similarities and dissimilarities between the properties of the nano particles and those of the bulk. We believe that these findings will be useful to understand correlation lengths deciding various properties of geometrical frustration and/or spin-chain phenomena.