Search

Abstract: The hyperfine environment of111Cd nuclei formed in the radioactive decay of111In ions implanted into CoO was studied via the PAC method. The quadrupole coupling constants measured in isochronal and isothermal annealing treatments at various oxygen pressures were related to the initial stages of the CoO→Co3O4 phase transition and interpreted as the successive trapping of cation vacancies at the111In probe. The phase transition was confirmed by X-ray diffraction, RBS and a PAC measurement on111Cd in spinel type Co3O4.

Abstract: The temperature dependence of the hyperfine field of substitutional111Cd in antiferromagnetic CoO has been measured by means of the perturbed angular correlation technique. The Larmor frequency ωL is found to obey a power law ωL(t=ω0 t β) up tot max=0.4 wheret=1−T/T N is the reduced temperature withT N=291.2(3) K and β=0.393 (5) the critical exponent. The results are discussed and compared with PAC experiments on111Cd in NiO and Ni and with results obtained by other methods.

The perturbed angular correlation (PAC) method was applied to study the temperature dependence of the magnetic hyperfine fields in111In-doped polycrystalline Fe3O4 and Co3O4. The critical behaviour near the magnetic phase transitions has been investigated. The changes occuring near the Vervey transition in Fe3O4 and the path of the supertransferred magnetic fied in Co3O4 are discussed. The results are compared with results obtained from Mössbauer spectroscopy.