ISSN:
1089-7550
Source:
AIP Digital Archive
Topics:
Physics
Notes:
As part of our effort to evaluate substituted barium ferrites for particulate magnetic recording,1 we have obtained room-temperature Mössbauer spectra for BaFe12−2xCoxTixO19 (CoTi), with x=0, 0.15, 0.30, 0.45, 0.60, 0.75, 0.80, 0.85, and 0.90. With increasing x, resolution steadily worsens as the 12-K lines broaden and change shape, but monotonic trends are evident for all spectral features, suggesting a gradual change in site occupation and local atomic environment. Following our earlier work on the well-resolved CoMo spectra (up to x=2.0),2 we have successfully fit a five-site Lorentzian model for x〈−0.45, however with the 12-K peak width varying independently of the other sites. A three-site model fits the main features of all spectra with a nearly linear decrease with x of hyperfine field (ionic moment) of ∼13%, 11%, and 9%, respectively, for the 4fvi, 4fiv, and 12-K sites, while the 12-K spectral area and hence site occupation increases; this is in contrast to CoMo, where the fields are independent of x and the 12-K area decreases with x. The correct fitting model is of course more complex than either of these, but is greatly clarified by the use of magnetically oriented absorbers with the gamma rays passing parallel to the magnetization direction. This procedure removes lines 2 and 5 from the sextet components and allows the full shape of 12-K lines 1 and 6 to be observed. We will discuss the results obtained in this way and relate them to trends in the bulk magnetic properties of CoTi-substituted barium ferrite.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.348341
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