Extracting the diffusivity ratio from point contact Andreev reflection spectroscopy and upper critical field measurements in MgB2

• Main Authors: Yates, Karen A., Miyoshi, Y., Grunwell, J., Riggall, K., Bugoslavsky, Y., Chen, Soo Kien, MacManus Driscoll, Judith L., Pogrebnyakov, A. V., Xi, X. X., Cohen, L. F.
• Format: Article
• Language: English; English
• Published: Institute of Physics 2008
• Online Access: http://psasir.upm.edu.my/id/eprint/6699/1/Extracting%20the%20diffusivity%20ratio%20from%20point%20contact%20Andreev%20reflection%20spectroscopy%20and%20upper%20critical%20field%20measurements%20in%20MgB2.pdf; http://psasir.upm.edu.my/id/eprint/6699/; http://dx.doi.org/10.1088/1742-6596/97/1/012213
• Institution: Universiti Putra Malaysia

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.