Antiferromagnetism inCaCu3Ti4O12studied by magnetic Raman spectroscopy

For ${\mathrm{CaCu}}_3{\mathrm{Ti}}_4{\mathrm{O}}_{12}$—an insulator that exhibits a giant dielectric response above 100 K—${\mathrm{Cu}}^{2+}$ antiferromagnetic spin ordering has been investigated by magnetic Raman scattering and magnetization measurements. Below the Néel temperature, $T_N=25\mathrm{}\mathrm{K},$ magnetic excitations have been identified. Above $T_N$ Raman spectra reveal short-range antiferromagnetic fluctuations that increase with cooling like $T^{-1}.$ No deviations from Curie-Weiss law have been observed above $T_N.$