${}^{95,97}\mathrm{Mo}$ NMR experiments have been performed on a series of ${\mathrm{Sr}}_2{\mathrm{FeMoO}}_6$ and electron-doped ${\mathrm{Sr}}_{2-x}{\mathrm{La}}_x{\mathrm{FeMoO}}_6$ ceramics. A detailed analysis of the NMR spectra from pristine ${\mathrm{Sr}}_2{\mathrm{FeMoO}}_6$ conclusively shows that the Mo hyperfine field is mainly due to atomic Mo magnetic moments. No contribution of transferred hyperfine field has been observed, confirming the absence of s electrons in the conduction band. Upon La doping, the NMR frequency (hyperfine field) gradually increases, proving that the concentration of spin-polarized electrons at a Mo ion is enhanced by the La substitution. A simple linear correlation between a magnetic moment at Mo sites and the Curie temperature of the system has been found. Implications for understanding the electronic structure and the ferromagnetic coupling in these systems are underlined.

• Received 14 October 2003

DOI:https://doi.org/10.1103/PhysRevB.69.100407