HoAs: a model compound for the cooling by the barocaloric effect

Recently a novel cooling technique has been introduced based on the barocal oric effect. The effect occurs in rare earth compounds where the crystallin e electric field splitting of the ran earth ion can easily be tuned by exte rnal pressure or uniaxial stress. As the positions of the low lying crystal line electric field levels have direct influence upon the thermodynamic pro perties of the system and hence its entropy, adiabatic cooling techniques c an be implemented. The monopnictide HoAs shows a barocaloric effect resulti ng from both a structural as well as a magnetic phase transition. Direct me asurements of the barocaloric effect in HoAs and inelastic neutron scatteri ng measurements of the crystalline electric field are presented. The observ ed barocaloric effect can well be explained by a model taking into account the effects of pressure upon the magnetism as well as upon the structure of the compound. (C) 2001 Elsevier Science B.V. All rights reserved.