Environmental effect on the magnetic properties of Fe ions in glasses and ceramics

The effect of the environment on the magnetic properties of Fe-ions in a sodium germanate glass, a sodium silicate glass, and in the same devitrified glasses has been studied. In the four samples investigated, the inverse magnetic susceptibility (X -1 ) follows a Curie-Weiss law behavior with a negative Curie temperature θ p indicating an antiferromagnetic interaction in the four samples. The measurements also revealed that |θ p | in both glass matrices is relatively low (<10 K) while in the crystalline samples it increased by 4-fold in the silicate and by about 20-fold in the germanate. The molecular field coefficients γ m are negative for all four samples. The γ m values for the Fe-germanate glass and the crystalline sample are 3 and 10 times larger than the corresponding values for Fe-silicate. These results reflect a stronger exchange interaction in the germanate (glass and crystalline) than the silicate samples.