The effect of Al doping on the structure and magnetism in cobaltite CaBaCo4O7

• Established the structural and magnetic phase diagram for CaBa (Co1−xAlx)4O7.
• Lattice and the spin degrees of freedom are relatively decoupled in CaBaCo4O7.
• Al doping suppresses short-range magnetic correlations which is observed well above TC in CaBaCo4O7.

We report the effects of Al-doping on the structure and magnetic properties in CaBa (Co1−xAlx)4O7 (0 ⩽ x ⩽ 0.25). The system exhibits a structural transition from an orthorhombic symmetry to a hexagonal symmetry when the Al content exceeds x = 0.1. The Curie temperature and the value of the magnetization decrease with increasing Al doping level, indicating that the ferrimagnetic ground state is gradually suppressed. The ground state eventually transits into a spin-glass state for x > 0.1. Moreover, the short-range magnetic correlations, which occur at high temperatures in CaBaCo4O7, are found to be gradually suppressed with increasing Al content and eventually disappear for x = 0.25. By comparing our results with other Co-site doping cases, we suggest that the lattice and the spin degrees of freedom are relatively decoupled in CaBaCo4O7.