Samarium magnetism studied on SmPd 2 Al 3 single crystal

In this paper, specific features of Sm magnetism in an intermetallic compound have been studied. For this purpose, a high-quality single crystal of ${\text{SmPd}}_{2}{\text{Al}}_{3}$ was grown and subjected to detailed measurements of specific heat, magnetization, ac susceptibility, and electrical resistivity with respect to temperature and a magnetic field applied along the principal crystallographic directions. ${\text{SmPd}}_{2}{\text{Al}}_{3}$ magnetism was found to be strongly anisotropic with the easy-magnetization direction along the $c$ axis where the main magnetic features are concentrated. The $a$-axis response remains weak, paramagneticlike, even in the magnetically ordered state. Ferromagnetism with ${T}_{C}=12.4\text{ }\text{K}$ has been indicated by all the measured physical properties. At lower temperatures, three successive order-order phase transitions have been observed on the temperature dependence of the specific heat as three anomalies: at 3.4, 3.9, and 4.4 K, respectively. The low-temperature magnetization data can be understood within a scenario that considers the antiferromagnetic ground state as being gradually destroyed through a series of four metamagnetic transitions at 0.03, 0.35, 0.5, and 0.75 T, as detected in the 1.8 K magnetization data. The temperature dependence of the paramagnetic susceptibility below 200 K can be in the first approximation interpreted in terms of a Curie-Weiss law modified by temperature-independent Van Vleck contribution due to the low-lying first excited multiplet $J=7/2$ being populated. At higher temperatures, involvement of the second excited multiplet $J=9/2$ should also be considered. The experimental data are discussed together with the results of electronic-structure and crystal-field calculations from first principles, which were performed as an important part of the study for comprehension and explanation of the observed behavior of the ${\text{SmPd}}_{2}{\text{Al}}_{3}$ compound.