Universal spin-glass behaviour in bulk LaNiO2, PrNiO2 and NdNiO2

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 AC 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.

Intrinsic magnetism in superconducting infinite-layer nickelates

“…This, together with the lack of ZF precession, suggests that the magnetic state is not static long-range ordered and that fluctuations (faster than the muon decay timescale) may be present and short-range correlations may dominate. This is consistent with previous reports of a lack of long-range order in the undoped infinite-layer nickelates [25][26][27].…”

Assessing the correlated electronic structure of lanthanum nickelates

“…Instead, we here want to briefly comment on the issue of ordered magnetism, since the spin physics of RENiO 2 compounds is highly puzzling in experiment. Absence of long-range order [41,93], quasi-static ordering [94], spin-glass physics [95], pseudogap vs. Curie-Weiss [96] and (para)magnon dispersions [97] are discussed. Various theoretical accounts [84,85,98] find a nearest-neighbor superexchange coupling J ∼ 60 − 70 meV, i.e.…”

Geometric effects in the infinite-layer nickelates

“…This circumstance has raised the question of the role of the 4f electrons [9] as well as of extrinsic factors such as the unintentional presence of topotatic hydrogen or apical oxygens, which have been argued to correlate with the structure [10,11]. Examining the RNiO 2 series for R from La to Lu as well as additional candidate materials for nickelate superconductivity has thus emerged as a consequential outlook [12][13][14][15][16][17][18][19][20][21][22][23][24]. At the same time, in analogy with their perovskite counterparts [25][26][27], the appearance of structural instabilities associated to the relative size of the R atom may also come into play as an additional key ingredient.…”