Mössbauer Studies on (Zn, Cd, Cu)0.5Ni0.5Fe2O4 Oxides

Abstract

The temperature dependence of the magnetic hyperfine fields on 57 Fe nuclei at the tetrahedral (A) and octahedral (B) interstitial sites in (Zn, Cd, Cu) 0.5 Ni 0.5 Fe 2 O 4 oxides have been investigated in Mössbauer measurements at sample temperatures ranging from 79 K to 850 K. The samples were prepared by solid-state reaction, and their phase determined from XRD measurements, which also provided information on their X-ray densities, grain sizes and lattice constants. The magnetic transition temperatures between ordered and paramagnetic states were obtained from zero-velocity measurements. The Cu 0.5 Ni 0.5 Fe 2 O 4 sample is found to be antiferromagnetic with Néel temperature of 823 K, and its super-exchange interactions, J AB , J AA and J BB were determined to be j24.14 k B , j13.10 k B and +11.68 k B , respectively. The (Zn, Cd) 0.5 Ni 0.5 Fe 2 O 4 are ferrimagnetic with Curie points of 543 and 548 K, respectively, and corresponding average exchange integrals J o = 186 k B and 188 k B .

Synthesis and magnetic properties of Cu0.5Ni0.5Fe2O4 nanoparticles produced by glycothermal and hydrothermal processes

“…This value compares well with the grain size of 44.45 ± 0.02 nm obtained for the bulk Cu 0.5 Ni 0.5 Fe 2 O 4 sample made by solid-state reaction [7]. The average lattice parameters of samples G and H were 8.36 ± 0.03 Å and 8.37 ± 0.01 Å respectively.…”

“…This disappears after sintering the sample at 900 • C. The narrowing of the peaks with increasing annealing temperature reflects increasing grain size. The grain sizes can be calculated from the broadening of the 311 XRD peak using the Scherrer formula [1,7,9]. The variation of grains size with sintering temperature is plotted in Fig.…”

“…Ferrites in the bulk form can be made by solid-state reaction from high purity oxides [5,7]. This method has the disadvantage of prolonged heat treatments at high temperatures.…”

Temperature dependence of the hyperfine fields in NiFe2O4 and CuFe2O4 oxides

“…The internal hyp erfine fields of B site Fe nuclei are higher than for those on A sites. This is in agreement with pr evious results [1,12]. The high values of hyp erfine fields below 300 K are con sistent with the 3+ oxidation state of Fe [1].…”

“…Mossbauer technique [12] and found to be 873 ± 3 K. A systematic decrease in hyperfine fields with increasing temperature (see Fig. 4) indicates a weakening of the magnetic coupling between the Fe ions.…”