Lattice Effect on the Superexchange Interaction in Antiferromagnetic Bi2.1Sr1.9CaCu2O8+δ

By employing Raman scattering and X-ray diffraction techniques on antiferromagnetic Bi2.1Sr1.9CaCu2O8+δ within the same pressure conditions, we tracked the evolution of the two-magnon spectrum and structural parameters under pressures of up to nearly 30 GPa. Consequently, we established the relationship between pressure, in-plane lattice parameter d, and superexchange interaction J as J ∼ d –(6.6±0.2). Within the examined pressure range, this compound did not exhibit superconductivity, as determined by a sensitive magnetic measurement technique. Additionally, we observed phonon anomalies, suggesting possible disorder effects in Bi–O layers and reduced charge transfer from these layers, particularly above 10 GPa. We discuss the impacts of pressure and chemical doping on J and the structure, along with their implications for superconductivity.