Magnetic correlations in subsystems of the misfit [Ca$_2$CoO$_3$]$_{0.62}$[CoO$_2$] cobaltate

摘要: [Ca$_2$CoO$_3$]$_{0.62}$[CoO$_2$], a two dimensional misfit metallic compound, is famous for its rich phases accessed by temperature, $i.e.$ high temperature spin-state transition, metal-insulator transition (MIT) at intermediate ($\sim$ 100 K) and low spin density wave (SDW). It enters into short range SDW phase below T$_{MIT}$ long completes 27 K [Phys. Rev. B 67, 104410 (2003)]. Information on independent role of layers (rocksalt/Ca$_2$CoO$_3$ \& triangular/CoO$_2$) in these scarce. By combining set complementary macroscopic (DC magnetization resistivity) microscopic (neutron diffraction X-ray absorption fine structure spectroscopy) measurements pure (CCO) Tb substituted the rocksalt layer CCO (CCO1), magnetic correlations both subsystems this compound are unraveled. found to exhibit glassiness, as well exchange bias (EB) effects, while CCO1 does not albeit it shows weaker EB effect. Our results show that magneto-crystalline anisotropy associated with acts source pinning, which responsible effect localization spins triangular (CoO$_2$) layer, giving rise glassiness CCO. local investigations from extended (EXAFS) spectroscopy neutron CCO, we also confirm arises CoO$_2$ layer.