Messungen an Fe57 in Calciumaluminatferriten mit Hilfe des Mößbauer-Effekts

Abstract

Measurements of the MÖSSBAUER-effect were made on Calcium-Aluminate-Ferrites [2 CaO · (Al2O3) x · (Fe2O3) 1-x] in the temperature range 4.2 °K ≦ Τ ≦ 700 °K. Ferrites with x=0, 1/3, 1/2 were made by sintering. The isomeric-shift is the same for the three ferrites, whereas the quadrupol-splitting is a function of x : ε1 (x=0) = (1.38 ± 0.05) mm/sec, ε2 (x=⅓) = (1.44 ± 0.05) mm/sec, ε3 (x =½) = (1.64 ± 0.05) mm/sec. The CURIE temperatures are Θ1 = (615 ± 4) °K, Θ2 = (490 ± 5) °K and Θ3= (398 ± 10) °K. For T=0 °K the extrapolated values of the magnetic field are independent of x : H0 (tet) = (505 ± 10) kOe and H0 (oct) = (555 ± 10) kOe at the tetrahedral and octahedral sites respectively. Under the assumption of an axial symmetric electric field gradient we calculated the angles between the electric field gradient and the magnetic field at the two lattice sites.