Extracting the diffusivity ratio from point contact Andreev reflection spectroscopy and upper critical field measurements in MgB2
Yates, Karen A. and Miyoshi, Y. and Grunwell, J. and Riggall, K. and Bugoslavsky, Y. and Chen, Soo Kien and MacManus Driscoll, Judith L. and Pogrebnyakov, A. V. and Xi, X. X. and Cohen, L. F. (2008) Extracting the diffusivity ratio from point contact Andreev reflection spectroscopy and upper critical field measurements in MgB2. Journal of Physics: Conference Series, 97 (1). 012213. ISSN 1742-6588
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Official URL: http://dx.doi.org/10.1088/1742-6596/97/1/012213
The di®usivity ratio ´, which measures the relative intraband scattering in the ¼ and ¾ bands in MgB2 has been determined by ¯tting the Hc2(T) at T » Tc and by Point Contact Andreev Re°ection. We ¯nd a satisfactory agreement between the values for ´ obtained by both methods for c-axis orientated MgB2 thin ¯lms. Point contact Andreev Re°ection was then applied to bulk MgB2 containing Mg vacancies. Spectra obtained in zero ¯eld indicate a distribution of the two gaps ¢¾;¼ but no merging of the values with increased magnesium de¯ciency. Spectra ¯tted as a function of ¯eld are consistent with an increase in ¼ intraband scattering with increasing magnesium de¯ciency. Measurement of the point contact Andreev re°ection spectra as a function of temperature revealed features not immediately expected from current theoretical models.
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