Anisotropic change in the crystal structure across the valence state transition in EuPd₂Si₂

Samples of EuPd₂Si₂ has been grown in an Arc furnace and annealed at 850 C for two weeks. The XRD measurements have confirmed the sample's purity and show that it has tetragonal I4/mmm crystal symmetry with the lattice parameter values consistent with the literature. Temperature-dependent DC field magnetization measurements show a valence state transition of Eu³⁺→Eu²⁺ near T_v = 142 K. The DC M-vs-T measurements show a minor shift of ≈1 K in the T_v with 6 T applied field. Furthermore, temperature-dependent powder and single-crystal XRD measurements showed that EuPd₂Si₂ has an anisotropic thermal expansion across T_v. The unit cell parameter c expands as temperature decreases while the parameter a and unit cell volume shrinks. The effect of the high magnetic field on crystal structure and valence state transition will be discussed.