Surface effect in antiferromagnetic Ba6Mn24O48 nanoribbons

Abstract

The magnetic properties of Ba6Mn24O48 nanoribbons and bulk are studied by zero-field-cooled and field-cooled magnetization, and ac susceptibility. Upon cooling, we find that both nanoribbons and bulk experience multiple magnetic phase transitions, i.e. paramagnetic, antiferromagnetic and re-entrant spin glass (RSG) phases at a low temperature. The main focus of this work is to understand the origin of RSG behaviour and to investigate the surface effect on magnetism in Ba6Mn24O48 nanoribbons. The dc susceptibility measurement shows that the paramagnetism in these nanoribbons involves the Curie–Weiss paramagnetism and temperature-independent contributions to magnetic susceptibility due to Pauli and Van Vleck paramagnetism. The Pauli paramagnetic contribution to susceptibility might give rise to uncompensated spins due to the breaking of sublattice pairing on the surface of nanoribbons. An exchange bias phenomenon is found in both Ba6Mn24O48 nanoribbons and bulk. The exchange field (HE) in the nanoribbons is larger than that of the corresponding bulk, which may also be induced by the uncompensated surface spins. The resistivity of Ba6Mn24O48 bulk presents the relation ln(ρ) ∝ T−1/2, and the possible conduction mechanism is suggested.