The effect of thermal treatment on superconductivity in HoNi2B2C

Rare-earth metal transition metal borocarbide and nitridoborate superconductors

“…Additionally, a variable boron content in the range 1 < x < 2 was determined in a study aiming to clarify the phase equilibria in the system [58]. Furthermore, a clear dependence of the physical properties, that means transition temperatures, electrical resistivity, and magnetic order [107][108][109], on the annealing history of the sample was traced back to formation of vacancies and to some disorder of C and B up to a considerable level of 8.6 %, based on neutron powder diffraction using YNi 2 [ 10 B 2 C] [110]. At this point it has to be mentioned that 11 B and C are nearly indistinguishable both in X-ray and neutron diffraction and 10 B with a clearly different diffraction length in neutron scattering is highly absorbing complicating the situation.…”

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.…”

“…Substituted atoms or vacancies on distinct lattice sites can either change the type of bonding or simply act as impurities scattering conducting electrons. These modifications may affect the spin ordering and the interaction with electron and, as a result, the superconducting properties [9,14].…”

“…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.%).…”