Pressure effect on the spin density wave transition in La2PrNi2O6.96

High-pressure studies reveal a stark contrast between the superconducting properties of double-layer Ruddlesden-Popper (RP) nickelates La₂⁢PrNi₂⁢O₇ and La₃⁢Ni₂⁢O₇. While La₂⁢PrNi₂⁢O₇ exhibits bulk superconductivity, La₃⁢Ni₂⁢O₇ displays filamentary behavior, suggesting that superconductivity is confined to phase interfaces rather than the bulk. Since magnetism emerges near the superconducting phase, understanding its differences in La₃⁢Ni₂⁢O₇ and La₂⁢PrNi₂⁢O₇ is essential for clarifying their underlying electronic and magnetic properties. 

In this work we study the magnetic responce of La₂⁢PrNi₂⁢O_6.96 under pressures up to 2.3 GPa using the muon-spin rotation/relaxation (𝜇⁢SR) technique. The application of external pressure increases the Néel temperature 𝑇_N from approximately 161 K at ambient pressure (𝑝=0) to about 170 K at 𝑝=2.30GPa. The temperature dependence of the internal magnetic field 𝐵_int⁡(𝑇) (i.e., the magnetic order parameter) follows the power-law relation 𝐵_int=𝐵_int⁡(0)⁢(1−[𝑇/𝑇_N]^𝛼)^𝛽, with consistent exponent values of 𝛼≃1.95 and 𝛽≃0.35 across different pressures. The value of the ordered moments at the Ni sites, which is proportional to 𝐵_int, remain unaffected by pressure. Our findings suggest that the magnetic properties of double-layer RP nickelate La₃⁢Ni₂⁢O₇ are broadly unaffected by Pr to La substitution. The slightly elevated Néel temperature for La₂⁢PrNi₂⁢O₇ compared to La₃⁢Ni₂⁢O₇ represents the most notable distinction, suggesting subtle effects arising from Pr substitution within the studied pressure range.