On the state and distribution of iron in the alnico 8 alloy

Mössbauer measurements have been carried out on Alnico 8 alloy after various heat treatments. The spectrum measured at room temperature (RT) of the sample heat treated for optimum permanent-magnet characteristics shows the presence of Fe in paramagnetic environment, with an average quadrupolar splitting Δ = 0.16 mm/s probably due to tetragonal distortion of the matrix. For the sample quenched and aged for 111 hours at 650°C the spectra measured at temperatures close to RT clearly show that the Curie point of the matrix is very near to RT. The obtained results allow us to interpret the behavior of saturation magnetization σ of the alloy as a function of the aging temperature. From Mössbauer measurements carried out on overaged samples the homogeneity characteristics of the phases are inferred.