Antiferromagnetism in CaCu 3 Ti 4 O 12 studied by magnetic Raman spectroscopy

For ${\mathrm{CaCu}}_{3}{\mathrm{Ti}}_{4}{\mathrm{O}}_{12}$\char22{}an insulator that exhibits a giant dielectric response above 100 K\char22{}${\mathrm{Cu}}^{2+}$ antiferromagnetic spin ordering has been investigated by magnetic Raman scattering and magnetization measurements. Below the N\'eel temperature, ${T}_{N}=25\mathrm{K},$ magnetic excitations have been identified. Above ${T}_{N}$ Raman spectra reveal short-range antiferromagnetic fluctuations that increase with cooling like ${T}^{\ensuremath{-}1}.$ No deviations from Curie-Weiss law have been observed above ${T}_{N}.$