(color online) (a) Raman spectra obtained at ∼ 20 K under pressure. (b) Slope of linear electronic background from 200–300 cm⁻¹ at ∼ 20 K. Spectra under pressure were normalized to the intensity at 850 cm⁻¹. (c) Pressure dependence of electron–phonon coupling parameter λ obtained by fitting the B_1g phonon using the theory of Ref. [12]. (d) Raman spectra of two-magnon peak at ∼ 20 K under pressure. The inset is the ratio of the integrated spectral weight below 1000 cm⁻¹ to that above 1000 cm⁻¹ for each pressure. Reprinted with permission from Ref. [9], copyright 2008 by the American Physical Society.