Investigation of structural and physical properties of trilayer nickelates - R₄Ni₃O₁₀ (R = La, Pr and Nd).

The Ruddlesden Popper nickelates with the general formula R_n+1Ni_nO_3n+1 (n = 1,2,3 and ∞) have seen a resurgence of interest due to the recent discovery of superconductivity in Nd_0.8Sr_0.2NiO₂ thin films¹. Moreover, ARPES studies on the n = 3 member(La₄Ni₃O₁₀) has revealed a large hole Fermi surface that closely resembles that of optimally hole doped cuprates². These nickelates, being structurally and electronically analogous to the HTSCs, provide an excellent platform to investigate the origin of superconductivity in HTSCs. Here we show the detailed investigation of the structure-property relationship in the trilayer nickelates - R₄Ni₃O₁₀ (R = La, Pr and Nd) across the metal-to-metal transition³ observed at T_MMT =135 K (La), 156 K(Pr) and 160 K(Nd). Distinct anomaly in the lattice parameters, magnetic susceptibility, transport and thermal expansion is seen at MMT, suggesting strong coupling between magnetic,electronic and structural degrees of freedom. The magnetic long range ordering in both R = Pr and Nd is highly suppressed despite a large value of θ_P, indicating the presence of strong frustration.
References :
1. Nature Letter pp. 7–11 (2019)
2. Nature Physics (2017)
3. Journal of Solid State Chemistry 117, 236 (1995)