NMR study of Y substitution effects in LaCo2B2

• Main Authors: Hsuan-yuChen, 陳軒宇
• Other Authors: Chin-Shan Lue
• Format: Others
• Language: zh-TW
• Published: 2015
• Online Access: http://ndltd.ncl.edu.tw/handle/16082038552418004008

碩士 === 國立成功大學 === 物理學系 === 103 === In recent studies, LaCo2B2 has attracted lots of attentions because of crystallizing in an iron-based superconductor like ThCr2Si2-type structure and emerging bulk superconductivity (Tc~4 K) by doping Y or Fe atoms. LaCo2B2 and YCo2B2 have been reported as a material with metallic electrical conductivity and Pauli paramagnetic behavior. However, there is little experimental effort associated with their local electrical structure features. In this study, we report an observation in LaCo2B2, La0.9Y0.1Co2B2 and YCo2B2 by using 59Co and 11B nuclear magnetic resonance (NMR) measurements. The 59Co NMR isotropic knight shift (59Kiso) is positive and close to each other, revealing that the Co-4s electrons and the orbital term are the major source. In addition, the 11B NMR isotropic knight shift (11Kiso)indicates an enhanced trend in B-2s density of state (DOS) and the contribution from orbital term. With the spin-lattice relaxation rate (1/T1) analyses, we found a strong similarity in the DOS of 59Co and11BbetweenLaCo2B2 and YCo2B2, indicating the uniformity in the electronic structure properties. Moreover, for La0.9Y0.1Co2B2, the 1/T1 analyses revealed a highly uplifted in B-2p DOS owing to the Y substitution effect that may account for the appearance of superconductivity.