Multiband superconductivity in HoNi2B2C

Crystal growth of rare earth-transition metal borocarbides and silicides

“…The anisotropy of H c2 (T) above T N results from enhanced pair breaking for HJ[1 1 0] due to interaction of Ho moments with conduction electrons. Note that H c2 (T) becomes isotropic below T N , which strongly suggests that superconductivity in C phase survives at a special Fermi surface sheet (FSS) which is isolated from the influence of the rare earth magnetism localized at another FSS [35].…”

Effect of B and C concentration on crystallization and properties of HoNi2B2C

“…All the samples were annealed at the same temperature (1100 • C) and quenched to eliminate the effect of atom site occupancies on variation of the physical properties, which was revealed in Refs. [10,14,17]. Therefore, under these conditions composition deviations of the HoNi 2 B 2 C phase are responsible for variation of superconducting properties.…”

“…Up to now, there is no general theory regarding the effect of mutual element substitution on lattice sites, which can explain the variation of superconducting properties in RENi 2 B 2 C primarily resulting from different heat treatments in polycrystalline [14] as well as in single crystalline HoNi 2 B 2 C samples [10]. Substituted atoms or vacancies on distinct lattice sites can either change the type of bonding or simply act as impurities scattering conducting electrons.…”

“…It can show three * Corresponding author. principal types of the superconducting behavior depending in the exact phase composition inside its homogeneity region and atomic site occupancies [8][9][10]. These are (i) plain superconductivity with T c around 8 K, (ii) normal conducting behavior, and (iii) superconducting transition with subsequent loss of the superconductivity between 5 and 6 K due to formation of incommensurate magnetic structures of Ho 3+ moments destructive to superconductivity and re-entrance of superconductivity below 5 K. In this latter re-entrant superconducting state both incommensurate magnetic structures are locked into a commensurate antiferromagnetic one at least down to 1.2 K [11].…”

“…the "chemical pressure", strongly affect on the superconducting and re-entrant features of the material obtained [12,13]. It was shown that the re-entrant behaviour in HoNi 2 B 2 C is very sensitive to composition variations and atomic site occupancies related to an appropriate thermal treatment of samples [9,10,14]. Even modern methods of element analysis exhibit the relative large errors of concentration determination for light elements such as B and C in RENi 2 B 2 C compounds (at least several at.%).…”