Giant reversible magnetocaloric effect in cobalt hydroxide nanoparticles

The magnetocaloric effect associated with magnetic phase transitions in β-Co(OH)2 nanoparticles has been investigated. A sign change in the magnetocaloric effect is induced by a magnetic field, which is related to a field-induced transition from the antiferromagnetic to the ferromagnetic state below the Néel temperature. The large reversible magnetic-entropy change −ΔSm (20.9 J/kg K at 15 K for a field change of 7 T) indicates that β-Co(OH)2 is a potential candidate for application in magnetic refrigeration in the low-temperature range.