Magnetotransport study of MgB₂superconductor

Abstract

Precise magnetotransport studies of heat and charge carriers in polycrystalline MgB 2 show that magnetic fields up to 8 T remarkably influence electrical resistivity, thermoelectric power and thermal conductivity. The superconducting transition temperature shifts from 39 K to 19 K at 8 T as observed on electric signals. The temperature transition width is weakly broadened. Electron and phonon contributions to the thermal conductivity are separated and discussed. The Debye temperature calculated from a phonon drag thermoelectric power component is inconsistent with values derived through other effects.

Physical property characterization of bulk MgB2 superconductor

“…In earlier reports the κ(T) of MgB 2 did not exhibit any sign of superconducting transition [13,33,38,42,45,51,52,55,56]. However on the contrary, recently the κ(T) data on pure and substituted MgB 2 single crystals had shown an anomaly in thermal conductivity below T c [57].…”

Фазовые переходы в гранулярном BCS-сверхпроводнике MgB-=SUB=-2-=/SUB=- в слабых магнитных полях

“…Однако справедливость подобного тезиса далеко не очевидна, и вопрос о влиянии температуры и внеш-него магнитного поля на характер эволюции вихревой структуры гранулярных BCS-сверхпроводников MgB 2 окончательно не решен. Несмотря на огромное коли-чество работ, посвященных попыткам построения фазо-вых H−T -диаграмм гранулярных BCS-сверхпроводников MgB 2 при низких температурах (см., например, [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21]), до сих пор не установлено положение линий H c1g (H c1A ) и H c2J на фазовой H−T -диаграмме. Более того, подвергается сомнению и само существова-ние " слабых связей" [иными словами, наличие линии H c2J (T ) на H−T -диаграмме] в случае гранулярного BCS-сверхпроводника MgB 2 [22][23][24][25][26][27][28].…”

“…5). 7 2. Скачки электросопротивления в подсистеме " сла-бых связей" в T C j значительно превышают скачки электросопротивления сверхпроводящих гранул в T cA (рис.…”

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.…”

“…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]). The general behavior of κ with T is that initially κ increases with T attaining a maximum value at some temperature T max .…”