Nota de FísicaPublicado
NMR Measurements in Compounds
K.M.B. Alves; N. Alves; Luiz C. Sampaio; S.F. da Cunha; A. P. Guimarães
1990
Dados da publicação
- Autores
- K.M.B. Alves; N. Alves; Luiz C. Sampaio; S.F. da Cunha; A. P. Guimarães
- Tipo
- Nota de Física
- Status
- Publicado
- Data de publicação
- 1990
- Descrição
- In a previous work, <math>^{89}Y\,\!</math> measurements at <math>4.2\,\!</math> <math>K\,\!</math> in <math>\;(R_xY_{1-x})Fe_2\,\!</math> compounds, with <math>R = Tb\,\!</math> and <math>Ho\,\!</math> and <math> 0.05 \leq \times \leq 0.20 \,\!</math> , have shown broad NMR spectra, due to transferred hyperfine interactions. <math>^{89}Y\,\!</math> NMR signals could not be observed with <math>R = Dy\,\!</math> in the same composition range. In the present work, compounds were prepared with dysprosium substitution in the concentration range <math> 0.005 \leq \times \leq 0.02 </math> to investigate the origin of this anomaly. Compared to the pure <math>\;YFe_2</math> compound, the observed NMR spectra are broadened and show a shift towards higher frequencies. With increasing <math>Dy\,\!</math> concentration, the NMR signals fall very rapidly. Measurement of relaxation times shows that the decrease in the signals cannot be attributed to a sharp increase in the nuclear relaxation rate due to the presence of <math>Dy\,\!</math> atoms in the matrix. Magnetization measurements at <math>4.2 K\,\!</math> were performed in samples with <math>Tb, Ho\,\!</math> and <math>Dy\,\!</math>; the results indicate that the behavior of the <math>Dy\,\!</math> compounds is qualitatively different in the low magnetic field region of the curves, requiring a minimum applied field to start increasing the magnetization. The NMR data and the magnetization results of the <math>Dy\,\!</math> compounds can both be explained as arising from a much lower mobility of the domain walls.
- Ano
- 1990
- Número
- CBPF-NF-002/90
- Vínculo com tese
- Não
- Vínculo com bolsa
- Não