Magnetic Properties of Quasi-One-Dimensional Lanthanide Calcium Oxyborates Ca4LnO(BO3)3.

This study examines the lanthanide calcium oxyborates Ca4LnO(BO3)3 (Ln = La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Y, Er, Yb). The reported monoclinic structure (space group Cm) was confirmed using powder X-ray diffraction. The magnetic Ln3+ ions are situated in well-separated chains parallel to the c axis in a quasi-one-dimensional array. Here we report the first bulk magnetic characterization of Ca4LnO(BO3)3 using magnetic susceptibility χ(T) and isothermal magnetization M(H) measurements at T ≥ 2 K. With the sole exception of Ca4TbO(BO3)3, which displays a transition at T = 3.6 K, no magnetic transitions occur above 2 K, and Curie-Weiss analysis indicates antiferromagnetic nearest-neighbor interactions for all samples. Calculation of the magnetic entropy change ΔSm indicates that Ca4GdO(BO3)3 and Ca4HoO(BO3)3 are viable magnetocaloric materials at liquid helium temperatures in the high-field and low-field regimes, respectively.