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December 08, 2012

Artificial and self-assembled pinning centers in Ba(Fe1-xCox)2As2 thin films as a route to very high current density

Arxiv - ABSTRACT - We report on the superior vortex pinning of single and multilayer Ba(Fe1-xCox)2As2 thin films with self-assembled c-axis and artificially introduced ab-plane pins. Ba(Fe1-xCox)2As2 can accept a very high density of pins (15-20 vol%) without Tc suppression. The matching field is greater than 12 T, producing a significant enhancement of the critical current density Jc, an almost isotropic Jc (Theta,20T) over 10^5 A/cm2, and global pinning force density Fp of ~ 50 GN/m3. This scenario strongly differs from the high temperature cuprates where the addition of pins without Tc suppression is limited to 2-4 vol%, leading to small HIrr enhancements and improved Jc only below 3-5 Tesla.
TEM images of HOC–S100 single layer Ba(Fe0.92Co0.08)2As2 thin film. (a)-(b), cross-section images showing the c-axis BFO-nanorods (NR) and the ab-arranged nanoparticles (NP). (c) Planar view reveals a high density of nanorods, corresponding to a matching field B=13.2T.



Jc as a function of applied field at high temperature for HOC-S50 and HOC-S100. Two field orientations are shown: (a) H//c and (b) H//ab.



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