Influence of carbon substitution on the heat transport in single crystallineMgB2

Abstract

We report data on the thermal conductivity κ(T, H) in the basal plane of hexagonal singlecrystalline and superconducting Mg(B1−xCx)2 (x = 0.03, 0.06) at temperatures between 0.5 and 50 K, and in external magnetic fields H between 0 and 50 kOe. The substitution of carbon for boron leads to a considerable reduction of the electronic heat transport, while the phonon thermal conductivity seems to be much less sensitive to impurities. The introduction of carbon enhances mostly the intraband scattering in the σ-band. In contrast to the previously observed anomalous behavior of pure MgB2, the Wiedemann-Franz law is valid for Mg(B0.94C0.06)2 at low temperatures.

Systematic study of the superconducting and normal-state properties of neutron-irradiatedMgB2

“…Arguments based on the temperature dependence of the anisotropy of the upper critical field suggest both carbon and aluminum doping increase scattering within the π band relative to the σ band, with the effect is much more pronounced in the case of carbon doping 7 . It should be noted that other researchers have concluded that changes in the temperature and magnetic field dependence of the thermal conductivity, κ(T,H), for carbon substituted single crystals are consistent with carbon doping resulting in an enhancement in intra-σ-band scattering 50 . Although there exists some debate as to the exact nature of the enhancement in scattering in carbon doped MgB 2 , it is clear that the development of H c2 is dominated by scattering effects for carbon substitutions and and Fermi surface changes effects for aluminum substitution.…”

Influence of carbon on intraband scattering in Mg(B 1-x C x ) 2

“…This conclusion is consistent with results presented in other reports, however there is no agreement which band is influenced by the carbon substitution. Some reports indicate that it is the  band [22,23,24], whereas others suggest the  band [25,26].…”

Hump structure below Tc in the thermal conductivity of MgB2 superconductor

“…There has been an intensive study of almost all the types of physical properties of the MgB 2 superconductor in both the super conducting and normal states, and thus sufficient progress has been made to understand the behavior of this compound [5]. In particular, the thermal conductivity has been investigated by a large number of workers [6][7][8][9][10][11][12][13][14][15][16] by considering various forms of the MgB 2 system, like different defect levels, different types of doping, and single or polycrystalline samples. The studies of the thermal conductivity (κ) of MgB 2 made by Sologubenko et al [9,13], Wu et al [15] and Anshukeva et al [16] is limited to low temperatures (T ≤ 100K) only and in these studies κ increases with temperature T within the considered temperature range.…”

“…In particular, the thermal conductivity has been investigated by a large number of workers [6][7][8][9][10][11][12][13][14][15][16] by considering various forms of the MgB 2 system, like different defect levels, different types of doping, and single or polycrystalline samples. The studies of the thermal conductivity (κ) of MgB 2 made by Sologubenko et al [9,13], Wu et al [15] and Anshukeva et al [16] is limited to low temperatures (T ≤ 100K) only and in these studies κ increases with temperature T within the considered temperature range. Other authors [6-8, 10-12, 14] have studied the thermal conductivity up to much higher temperature range (T ≤ 250K [7], T ≤ 275K [10,11], T ≤ 300K [6,8,12,14]).…”