Abstract
Motivated by the recent discovery of superconductivity in infinite-layer nickelate thin films, we report on a synthesis and magnetization study on bulk samples of the parent compounds RNiO2 (R = La, Pr, Nd). The frequency-dependent peaks of the alternating current magnetic susceptibility, along with remarkable memory effects, characterize spin-glass states. Furthermore, various phenomenological parameters via different spin glass models show strong similarity within these three compounds as well as with other rare-earth metal nickelates. The universal spin-glass behaviour distinguishes the nickelates from the parent compound CaCuO2 of cuprate superconductors, which has the same crystal structure and d 9 electronic configuration but undergoes a long-range antiferromagnetic order. Our investigations may indicate a distinctly different nature of magnetism and superconductivity in the bulk nickelates than in the cuprates.
Highlights
The nickelates are widely believed to be promising candidates for unconventional superconductors because of their very similar structures and possibly related electronic states to the cuprates
Strain effects may play an important role in the superconductivity of thin films, where a 3% larger c-axis lattice constant affects the Ni dz2 orbital which may be crucial for nickelate superconductivity[9, 12, 13]
Theoretical calculations propose that the 4f electrons have an important influence on the electronic structure through 4f -5d interactions[27,28,29], the doped LaNiO2 thin films have recently been shown to superconduct[3, 4]
Summary
The nickelates are widely believed to be promising candidates for unconventional superconductors because of their very similar structures and possibly related electronic states to the cuprates. Sr- and Ca-doped LaNiO2 thin films[3, 4] have been shown to be superconducting.This discoveries have aroused intensive research and discussions, First, superconductivity is absent in bulk samples, e.g. in bulk Nd1−xSrxNiO2[5, 6] and Sm1−xSrxNiO2[7], and no signs of long-range magnetic orders have been observed. This discrepancy between non-superconducting bulk samples and superconducting thin films has not been well understood so far. Theoretical calculations propose that the 4f electrons have an important influence on the electronic structure through 4f -5d interactions[27,28,29], the doped LaNiO2 thin films have recently been shown to superconduct[3, 4]
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