Magnetic properties of monoclinic lanthanide orthoborates, LnBO<inf>3</inf>, Ln = Gd, Tb, Dy, Ho, Er, Yb

Abstract

© 2017 Elsevier Ltd The lanthanide orthoborates, LnBO 3 , Ln = Gd, Tb, Dy, Ho, Er, Yb crystallise in a monoclinic structure with the magnetic Ln 3+ forming an edge-sharing triangular lattice. The triangles are scalene, however all deviations from the ideal equilateral geometry are less than 1.5%. The bulk magnetic properties are studied using magnetic susceptibility, specific heat and isothermal magnetisation measurements. Heat capacity measurements show ordering features at T ≤ 2 K for Ln = Gd, Tb, Dy, Er. No ordering is observed for YbBO 3 at T ≥ 0.4 K and HoBO 3 is proposed to have a non-magnetic singlet state. Isothermal magnetisation measurements indicate isotropic Gd 3+ spins and strong single-ion anisotropy for the other Ln 3+ . The change in magnetic entropy has been evaluated to determine the magnetocaloric effect in these materials. GdBO 3 and DyBO 3 are found to be competitive magnetocaloric materials in the liquid helium temperature regime.