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The57Fe Mo¨ssbauer spectra of oriented single‐crystal and powder PbFe12O19(abstract)

 

作者: B. J. Evans,   G. K. Thompson,  

 

期刊: Journal of Applied Physics  (AIP Available online 1991)
卷期: Volume 69, issue 8  

页码: 6231-6231

 

ISSN:0021-8979

 

年代: 1991

 

DOI:10.1063/1.348818

 

出版商: AIP

 

数据来源: AIP

 

摘要:

The recent determination of the crystal structure of PbFe12O19by means of single‐crystal x‐ray diffraction has made it possible to carry out a definitive and comparative analysis of the structure‐property relationship of PbFe12O19, SrFe12O19, and BaFe12O19. We have therefore performed57Fe Mo¨ssbauer measurements on oriented, single‐crystal, and powder samples of PbFe12O19at 298 K. For a single‐crystal oriented parallel to thecaxis, five distinct patterns are observed. The hyperfine fields, isomer shifts, and quadrupole interactions are as follows: 12k:Heff=413 kOe; &dgr;=0.33 mm s−1; &Dgr;=0.35 mm s−1; 4f1: 487 kOe; 0.24 mm s−1; 0.13 mm s−1; 4f2: 514 kOe; 0.39 mm s−1; 0.29 mm s−1; 2a: 496 kOe; 0.30 mm s−1; 0.11 mm s−1; 2b: 399 kOe; 0.30 mm s−1; 2.00 mm s−1. The relative magnitude of each of these parameters is in good agreement with and exhibits the same trend observed for high‐purity SrFe12O19. The relative intensity of the 2bpattern for the crystal oriented parallel to thecaxis is 8.2%, which approaches its theoretical value; of the total number of iron ions in the structure, 8.33% of them occupy the 2bsite. The value for the polycrystalline sample is only 5.4% of the total intensity. However, for a single crystal oriented perpendicular to thecaxis, the 2bpattern exhibits a negligible intensity within the experimental error. This result confirms the dynamic disorder in the position of the 2biron ions and suggests a stronger anisotropy for the case of PbFe12O19than for SrFe12O19and BaFe12O19. Even though the trend in hyperfine parameters at 298 K is similar to Sr, Ba, and Pb hexaferrites, PbFe12O19exhibits hyperfine fields that are consistently lower than those of the Ba and Sr analogues. This result is discussed in terms of the Curie temperatures, magnetic exchange interactions, and structural parameters. 

 

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