Observation by mössbauer spectroscopy of electron hoppings in the spinel series Zn1-xGexFe2O4

The Mössbauer spectra of the spinel series Zn_1-xGe_xFe₂O₄ with x = 0.25, 0.5 and 0.75 are observed between 77 and 623 K. In the detection limit of the Mössbauer spectrometry, the ferrous and ferric ions are all found on the B sites and the broadening of the spectra between the Curie point and 623 K is correlated with an electron hopping process via a conduction band. This process favors a “double exchange” which can explain the magnetic order in the compounds with x = 0.25 and x = 0.5 below 200 and 250 K.