Chemical Substitution Effect of High-T_c Superconductor Candidate R₄Ni₃O₈ (R: Rare-earth)

Abstract

R 4 Ni 3 O 8 (R: rare-earth) is a candidate for high-T c superconductor because its crystal structure and electronic state are very similar to high-T c cuprates. Our recent works have pointed out that, by intercalation-deintercalation treatment with sulfur, the additional oxygen which impedes the metallic conduction is removed and the metallic behavior shows up in Nd 3.5 Sm 0.5 Ni 3 O 8. However, the semiconducting tendency remains below about 20-40 K, suggesting that the removal of additional oxygen is not complete. In this study, Pr-doping to Nd site in Nd 4 Ni 3 O 8 was performed in order to completely remove additional oxygen. By Pr-substitution, the electrical resistivity decreases and maintains metallic behavior down to low temperature (2 K). Next, we performed carrier tuning by chemical substitution to Ni sites in order to bring the electronic states of Ni closer to that of Cu in high-T c cuprates. Although the resistivity increases by doping, metallic behavior is maintained, suggesting that the dopants might occupy the specific Ni sites. However, superconductivity is not observed down to 2 K.

Short-range magnetic interactions and spin-glass behavior in the quasi-two-dimensional nickelate Pr4Ni3O8

“…NMR measurements revealed 2D antiferromagnetic fluctuations [22], and both magnetic and chargeordering phenomena were inferred from x-ray and neutrondiffraction (ND) measurements [23,24]. Semiconducting behavior has also been reported for Nd 3.5 Sm 0.5 Ni 3 O 8 , with a trend to increasing metallicity under pressure [25], while the metallicity of Pr z Nd 4−z Ni 3 O 8 was reported to increase with Pr content z [26].…”

“…2 we show the temperature dependence of both contributions. The high-temperature part of the linear paramagnetic susceptibility above ≈ 160 K can be well fitted by a Néel-type law, χ para (T ) = C/(T + ) + χ 0 , with a Curie constant C ≈ 6.8 emu K Oe −1 mol −1 , a Pauli-paramagnetic susceptibility χ 0 ≈ 10 −3 emu Oe −1 mol −1 , and ≈ 160 K. If we assume the free-ion value for the magnetic moment of Pr 3+ (3.58 μ B ) as has been found in Pr 4 Ni 3 O 10 [26,27], we obtain a residual magnetic moment of ≈ 1.70 μ B . This value would be consistent with the localized moment of one spin-1/2 Ni + ion, but most probably rather represents an average over the three Ni sites [12], with some delocalized 3d electrons that lead to the observed metallic behavior.…”

Limits to the strain engineering of layered square-planar nickelate thin films

“…Nevertheless, La 1−x Ca x NiO 2 and Pr 4 Ni 3 O 8 35 single crystals are metallic but not yet superconducting to date. In contrast, most reduced infinite-layer [32][33][34]77 and layered nickelate powders [19][20][21][22][78][79][80] are insulating-metallic (Pr, Nd) 4 Ni 3 O 8 pellets were, however, achieved with reductions using a sulfur getter to promote the removal of apical oxygens 81,82 . Thus metallicity in square-planar, or T 0 , nickelates may be exquisitely sensitive to the oxygen content like in T 0 cuprates 83 .…”

Competing spin-glass and spin-fluctuation states in NdxPr4−xNi3O8

“…Moreover, Sm-substituted Nd 3.5 Sm 0.5 Ni 3 O 8 samples show no change in their electrical behavior as compared to unsubstituted samples, even at a high pressure up to 2 GPa [34]. Pr-substituted Nd x Pr 4−x Ni 3 O 8 samples exhibit metallic behavior and a positive correlation between resistivity and Nd content x [35]. [36].…”