Magnetic spin interactions observed by heat capacity measurements for layered compounds: NaLnTiO4 (Ln = Sm, Eu, Gd, Tb, Dy, Ho and Er)

Abstract Magnetic properties of a series of orthorhombic Na Ln TiO 4 ( Ln  = Sm, Eu, Gd, Tb, Dy, Ho and Er) characterized by heat capacity measurements are reported. Magnetic transitions are observed for all Na Ln TiO 4 investigated except for Ln  = Eu. The change in magnetic entropy closely agrees with the expected theoretical values except for Ln  = Sm and Gd. Peak profiles in temperature dependence of heat capacity indicate that Ln  = Sm, Tb, Dy, Ho and Er phases possess Ising square lattices. Furthermore, Ln  = Gd also exhibits the similar property regardless of its S state; there seems some degree of anisotropy in its magnetic lattice. Magnetization and heat capacity data indicate that superexchange through oxygen is the dominant spin interaction in this system.