Large, Homogeneous, and Isotropic Critical Current Density in Oxygen-Annealed Fe_1+yTe_0.6Se_0.4Single Crystal

Abstract

We reported a controllable way of removing excess Fe in Fe 1+y Te 0.6 Se 0.4 by annealing in a fixed amount of O 2 . Compared with the weak superconductivity induced by dilute acids, O 2 annealing can successfully induce bulk superconductivity. Proper O 2 annealing changes the temperature dependence of resistivity at low temperatures from semiconducting to metallic, which comes from the deintercalation of excess Fe. Critical current densities with field along the c-axis and ab-plane are found almost isotropic with large values of // Hc c

Effects of heavy-ion irradiation on FeSe

“…5 (right axis), the self-field J c at 2 K is increased about 5 times from ∼4×10 4 A/cm 2 for the pristine crystal to ∼2×10 5 A/cm 2 for the crystals with B φ = 2 T. Such a large value of enhanced J c is already close to that reported in high-quality FeTe 1−x Se x single crystals [55,56]. For B φ > 2 T, the value of J c is gradually suppressed with the increase in columnar defects.…”

Effects of Iodine Annealing on Fe1+yTe0.6Se0.4

“…Figure 3(c) summarizes the evolution of T c and the self-field J c (2 K) with the molar ratio of iodine. T c reaches the highest value of 14.5 K when annealing in 6.7% iodine and J c is up to 5×10 5 A/cm 2 after annealing in 5.6% iodine under a self-field at 2 K, which is larger than those reported for Fe(Te,Se) [10,[21][22][23][24][25][26] and similar to the highest reported value for oxygen-annealed Fe 1+y Te 0.6 Se 0.4 [13,27]. It has been proved that such a large J c cannot be obtained from the superconductivity only near the surface [13], which indicates that the sample maintaining such a large J c obtained in our experiment must be a bulk superconductor.…”

Magneto-optical characterizations of FeTe0.5Se0.5thin films with critical current density over 1 MA cm−2

“…In Figure 5, we compare the temperature dependence of J c 's for FeTe 0.5 Se 0.5 thin films grown on LAO and YSZ substrates together with that from high-quality single crystal, which also manifests a roof-top pattern in MO images [15,23]. The values of J c 's for thin films are over 10 6 A/cm 2 , one order of magnitude higher than that of the single crystal.…”

“…Magneto-optical (MO) imaging has proven to be extremely powerful for such purposes. It can visualize the spatial distribution of J c , and is widely used to study the connectivity between grains in IBSs [6,11,12,13,14,15,16]. In this report, we carefully studied the critical current density and its distribution in FeTe 0.5 Se 0.5 thin films by MO imaging for the first time.…”