Analysis of magnetization relaxation in MgB2 bulk samples obtained by electric-field assisted sintering

Fabrication and properties of denseex situmagnesium diboride bulk material synthesized using spark plasma sintering

“…The superconducting properties of the bulk samples were measured by the magnetization method using a VSM. T c,onset was measured as approximately 32 K using the AC susceptibility method in a magnetic field of 0.5 T. The depression of T c,onset when measured in a magnetic field of 0.5 T is expected; comparison with Frederick et al [24] indicates that carrying out measurements at 1 T would be expected to reduce T c,onset by around 5 K compared to the value at 0 T. In measurements carried out at 4 K on the sample prepared at higher pressure some jumps in the magnetization loops were seen due to flux jumping (figure 7), similar to those seen by Yanmaz et al [25], Miu et al [26] and Goeckner et al [27]. In this particular data set, these jumps occur at −1.4, −0.12, 0.0067 and 1.3 T and are thought to be sensitive to the magnetic sweep rate [25].…”

Microwave Synthesis of Fullerene-Doped MgB2

“…This is partly because of a higher rate of intake of C 60 into the lattice of MgB 2 from the SPS sample, as already discussed, and also because of a higher density of the SPS processed sample (Table ). Although the SPS sample (B7) has better functional characteristics ( J c and H irr ), its morphology and high density characteristics do not provide conditions for thermal versus magnetic compensation . Detrimental macroscopic flux jumps occur in the SPS sample at applied fields H of up to 1.6 × 10 6 A/m [on the ascending branch of the m ( H ) loops] at <10 K. For our MW samples (B5 and B6), macro jumps were not observed in the magnetization loops (Figure b, inset).…”

“…Although the SPS sample (B7) has better functional characteristics (J c and H irr ), its morphology and high density characteristics do not provide conditions for thermal versus magnetic compensation. 20 Detrimental macroscopic flux jumps occur in the SPS sample 10 at applied fields H of up to 1.6 × 10 6 A/m [on the ascending branch of the m(H) loops] at <10 K. For our MW samples (B5 and B6), macro jumps were not observed in the magnetization loops (Figure 4b, inset). However, samples obtained by MW and SPS show undesired microscopic flux jumps.…”

Relaxation and pinning in spark-plasma sintered MgB2superconductor

“…In this way, two magnetization loops measured at different field sweep rates provide direct information on the relaxation behavior in the whole investigated field range. We note that the dynamic logarithmic relaxation rate is equivalent to the conventional normalized logarithmic relaxation rate, = − , where t is the relaxation time [10,11,[14][15][16][17][18][19]. It can be seen in Table 1, where our results are compared to those of conventional relaxation in Ref.…”