Magnetic properties of the quasi-1D magnesium lanthanide borates Mg L n B 5 O 10

Abstract Lanthanide borates are widely studied for their optical and magnetic properties. A wide variety of structures are known with 3, 2, 1 and 0 dimensional connectivity of lanthanide ions. Here, we explore Mg L n B 5 O 10 , with a quasi-1D arrangement of the Ln ions. Polycrystalline samples of Mg L n B 5 O 10 ( Ln = La, Pr, Nd, Sm–Er) were synthesised via a solution-based method, which achieved higher purity than a solid-state method. Powder x-ray diffraction data confirmed the reported monoclinic space group ( P 2 1 / c ). The magnetic L n 3 + ions in Mg L n B 5 O 10 form relatively isolated zig-zag chains parallel to the b axis. Magnetic susceptibility and isothermal magnetisation were measured: all samples except L n = (Eu, Sm) fit the Curie-Weiss Law in isothermal magnetisation at high temperatures, in broad agreement with theoretical expectations. L n = (Nd, Tb, Dy, Ho, Er) exhibit signatures characteristic of Ising spin saturation, implying single ion anisotropy, while Gd exhibits characteristics of Heisenberg spins. Estimation of magnetic interactions suggests that Mg L n B 5 O 10 are candidate materials for quasi-1D magnetism. The magnetocaloric entropy change was also calculated, with MgGdB 5 O 10 showing promise for application to solid-state refrigeration at liquid helium temperatures.