Browsing by Author "Yeshurun, Y."

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Peak effect and the rhomb to square structural transition in the vortex lattice
(2006)
Bruckental, Y.
;
Rosenstein, B.
;
Shapiro, B. Ya.
;
Shapiro, I.
;
Shaulov, A.
The theory of structural transformation of the vortex lattice in a fourfold symmetric type II superconductor in the presence of both thermal fluctuations and quenched disorder is constructed. We show that in the absence of pinning, the slope of the square to rhomb transition in the T-H plane is generally negative: thermal fluctuations favor a more symmetric square lattice. Disorder\'s influence on the slope is just the opposite- it favors a less symmetric rhombic phase in which the fourfold symmetry is spontaneously broken. The second magnetization peak line in LaSCO in a wide range of doping is well described as a result of the transition.
Possibility of vortex lattice structural phase transition in the superconducting pnictide Ba(Fe(0.925)Co(0.075))(2)As(2)
(2010-03-01)
Kopeliansky, R.
;
Shaulov, A.
;
Shapiro, B. Ya.
;
Yeshurun, Y.
;
Rosenstein, B.
We present magnetic measurements in a single crystal of the newly discovered superconducting ironpnictide Ba(Fe(0.925)Co(0.075))(2)As(2). The magnetization loops exhibit a second magnetization peak (SMP) similar to that observed in most high-temperature superconductors (HTSs). Magnetic relaxation measurements reveal a minimum in the normalized relaxation rate, S = d ln M/d ln t, located in between the SMP onset and the peak fields. The SMP in HTSs is commonly associated with the vortex order-disorder phase transition. However, in Ba(Fe(0.925)Co(0.075))(2)As(2) the onset and peak fields, as well as the minimum point in S, exhibit strong temperature dependence down to low temperatures, excluding the possibility for such a transition. We suggest that the SMP in Ba(Fe(0.925)Co(0.075))(2)As(2) is associated with a vortex structural phase transition from rhombic to square lattice taking place at field and temperatures corresponding to the minimum point of S. A theoretical fit to the transition line, based on a recent theoretical model for vortex structural phase transition, shows good agreement with the experimental results.
Possibility of vortex lattice structural phase transition in the superconducting pnictide Ba(Fe0.925Co0.075)(2)As-2
(2010-03-01)
Kopeliansky, R.
;
Shaulov, A.
;
Shapiro, B. Ya.
;
Yeshurun, Y.
;
Rosenstein, B.
We present magnetic measurements in a single crystal of the newly discovered superconducting ironpnictide Ba(Fe0.925Co0.075)(2)As-2. The magnetization loops exhibit a second magnetization peak (SMP) similar to that observed in most high-temperature superconductors (HTSs). Magnetic relaxation measurements reveal a minimum in the normalized relaxation rate, S = d ln M/d ln t, located in between the SMP onset and the peak fields. The SMP in HTSs is commonly associated with the vortex order-disorder phase transition. However, in Ba(Fe0.925Co0.075)(2)As-2 the onset and peak fields, as well as the minimum point in S, exhibit strong temperature dependence down to low temperatures, excluding the possibility for such a transition. We suggest that the SMP in Ba(Fe0.925Co0.075)(2)As-2 is associated with a vortex structural phase transition from rhombic to square lattice taking place at field and temperatures corresponding to the minimum point of S. A theoretical fit to the transition line, based on a recent theoretical model for vortex structural phase transition, shows good agreement with the experimental results.