Pinning force scaling analysis of Fe-based high- T_c superconductors

Pinning force data, F_p, of a variety of Fe-based high-T_c superconductors (11-, 111-, 122- and 1111-type) were analyzed by means of a scaling approach based on own experimental data and an extensive collection of literature data. The literature data were mostly replotted, but also converted from critical current measurements together with data for the irreversibility line when available from the same authors. Using the scaling approaches of Dew-Hughes [J. Appl. Phys. 44, 1360 (1973)] and Kramer [Philos. Mag. 30, 293 (1974)], we determined the scaling behavior and the best fits to the theory. The data of most experiments analyzed show a good scaling behavior at high temperatures when plotting the normalized pinning force F_p/F_p,max versus the irreversibility field, Hirr. The resulting peak positions, h0, were found at ≈ 0.3 for the 11-type materials, at ≈ 0.48 for the 111-type materials, between 0.32 and 0.5 for the 1111-type materials and between 0.25 and 0.71 for the 122-type materials. Compared to the typical results of Bi₂Sr₂CaCu₂O_8+δ (h₀ ≈ 0.22) and YBa₂Cu₃O_7-δ (h₀ ≈ 0.33), most of the 122 and 1111 samples investigated show peak values higher than 0.4, which is similar to the data obtained on the light-rare earth 123-type HTSC like NdBa₂Cu₃O_y. This high peak position ensures a good performance of the materials in high applied magnetic fields and is, therefore, a very promising result concerning the possible applications of the Fe-based high-T_c superconductors.