NMR evidence for selective enhancement of Mo magnetic moment by electron doping in SrxLa2-xFeMoO6

95, 97Mo NMR experiments have been performed on a series of Sr2FeMoO6 and electron-doped Sr2-xLaxFeMoO6 ceramics. Detailed analysis of the NMR spectra from pristine Sr2FeMoO6 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 Mo ion is enhanced by the La substitution. A simple linear correlation between 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.