Dielectric anomalies and magnetodielectric coupling behavior of single crystalline Ca3Co2O6, a geometrically frustrated magnetic spin-chain system

摘要

The dielectric behavior of the single crystals of the spin-chain systemCa3Co2O6, undergoing geometrically frustrated antiferromagnetic ordering below25 K, has been investigated as a function of temperature and magnetic field (H)and compared with magnetization (M) behavior. The results provide evidence foranisotropic magnetodielectric (MDE) coupling in this compound. Acsusceptibility exhibits a strong frequency dependence for H parallel c withchanges of this feature with the application of external dc magnetic field. Nofeature in ac susceptibility could be observed for H perpendicular c, therebyproviding evidence for strong anisotropic spin-glass behavior. Interestingly,the strong frequency dependence in dielectric is present for both thecrystallographic directions (E parallel c and E perpendicular c where E is theelectric field) with a negligible influence of H, despite the existence of MDEcoupling. This result appears to suggest different dynamics of electric dipoleand spin-glass, although they are coupled with each other. In addition,interestingly, there is also a step at one-third of high-(magnetic) field valueof MDE at some temperatures tracking a similar step in M(H). This work alsoconfirms following unusual features reported on polycrystals, when measuredalong c-axis. The dielectric constant exhibits a broad peak around 50-130 Kwhen the electric field is applied along the spin-chain (crystallographic cdirection); however this feature is essentially absent for the perpendicularorientation. This finding supports the role of incipient spin-chain ordering toinduce magnetodielectric coupling. There is a signature of magnetoelectricphase coexistence when the magnetic field is applied along the spin-chainirrespective of the direction of applied electric field.