Contrasting physical properties of the trilayer nickelates Nd4Ni3O10 and Nd4Ni3O8

We report the crystal structures and physical properties of trilayer nickelates Nd 4 Ni 3 O 10 and Nd 4 Ni 3 O 8 . Measurements of magnetization and electrical resistivity display contrasting behaviors in the two compounds. Nd 4 Ni 3 O 10 shows a paramagnetic metallic behavior with a metal-to-metal phase transition ( T *) at about 162 K, as revealed by both magnetic susceptibility and resistivity. Further magnetoresistance and Hall coefficient results show a negative magnetoresistance at low temperatures and the carrier type of Nd 4 Ni 3 O 10 is dominated by hole-type charge carriers. The significant enhancement of Hall coefficient and resistivity below T* suggests that effective charge carrier density decreases when cooling through the transition temperature. In contrast, Nd 4 Ni 3 O 8 shows an insulating behavior. In addition, this compound shows a paramagnetic behavior with the similar magnetic moment as that of Nd 4 Ni 3 O 10 derived from the Curie-Weiss fitting. This may suggest that the magnetic moments in both systems are contributed by Nd 3+ ions. By applying pressures up to about 49 GPa, the insulating behavior is still present and becomes even stronger under a high pressure. Our results suggest that the different Ni configurations (Ni 1+/2+ or Ni 2+/3+ ) and the changes of coordination environment of Ni sites may account for the contrasting behaviors in trilayer nickelates Nd 4 Ni 3 O 10 and Nd 4 Ni 3 O 8 .