Stoichiometry, Spin Fluctuations, and Superconductivity in LaNiPO

TL;DR

This study investigates how slight non-stoichiometry affects superconductivity and spin fluctuations in LaNiPO, revealing that small compositional changes significantly impact its superconducting and magnetic properties.

Contribution

It provides new insights into the effects of non-stoichiometry and spin fluctuations on superconductivity in LaNiPO, comparing it with related nickel-based superconductors.

Findings

Superconductivity is sensitive to ~5% non-stoichiometry on La site.

All samples show ferromagnetic spin fluctuations around 14 K.

Electronic heat capacity increases with non-stoichiometry.

Abstract

Superconductivity in LaNiPO is disrupted by small (~5%) amounts of non-stoichiometry on the lanthanum site, even though the electronic contribution to the heat capacity increases with increasing non-stoichiometry. All samples also exhibit specific heat anomalies consistent with the presence of ferromagnetic spin fluctuations (Tsf ~ 14 K). Comparison of layered nickel phosphide and nickel borocarbide superconductors reveals different structure-property correlations in the two families.