Oxygen isotope effect on the AFM–FM phase transition of the layered cobaltite [formula omitted

Abstract

Zero-field muon spin rotation ( ZF – μ SR ) and DC magnetization investigations have been performed on the antiferromagnetic-ferromagnetic (AFM–FM) and the ferromagnetic-paramagnetic (FM–PM) transitions of two oxygen isotope ( 16 O or 18 O) substituted HoBaCo 2 O 5.47 powders. While the FM–PM phase transition shows nearly no isotope effect, a small but clear shift of 1.5 K on the transition temperature is observed for the AFM–FM transition. Together with the recent observation of an isotope effect on the metal–insulator transition on the same sample [E. Pomjakushina, et al., Phys. Rev. B 73 (2006) 113105.], our observations clearly show the coupling of electronic, magnetic and structural degrees of freedom in this system.