High‐quality Ni 3 Te 2 single crystals with length up to 6 mm are successfully grown by the physical vapor transport (PVT) technique. The crystals exhibit unique tubular structures with a hexagonal cross section. The high‐quality crystal is studied by a series of structural and morphological characterization. The physical properties including both magnetization and electrical transport are studied in detail. It is found that there exists a coexistence of weak ferromagnetism and antiferromagnetism at low temperatures. In the measured temperature range of 2–300 K, Ni 3 Te 2 shows a typical metallic behavior, and the temperature dependence of the resistivity ρ x x (T) can be well fitted by the parallel‐resistor model.

Multicomponent superconductors exhibit nontrivial vortex behaviors due to the various vortex-vortex interactions, including the competing one in the recently proposed type-1.5 superconductor. However, potential candidate that can be used to study the multicomponent superconductivity is rare. Here, we prepared an artificial superconducting multilayer to act as an alternative approach to study multicomponent superconductivity. The additional repulsive length and the coupling strength among superconducting films were regulated by changing the thickness of the insulting layer. The magnetization measurements were performed to clarify the effect of the competition between the repulsive vortex interactions on the macroscopic superconductivity. The vortex phase diagram and the optimum critical current density have been determined. Furthermore, a second magnetization effect is observed, and is attributed to the upper layer, which provides the weak pinning sites to localize the flux lines. The pinning behaviors switches to the mixed type with the increase of the insulting layer thicknesses. Our results open a new perspective to the study and related applications of the multilayer superconducting systems.

Systematic ac susceptibility measurements have been preformed to study the flux dynamics in a high quality KCa2Fe4As4F2 single crystal. The irreversible line in the vortex diagram is closed to theHc2 (T) line suggesting the strong intrinsic pinning in this material. The critical field Hcr = 0.4 T between single vortex pinning state and collective pinning state is obtained according to thermally activated flux creep model. The abnormal behavior in the single vortex pinning region that the activation energy U follows a ∽ H -0.53 dependence might arise from the planar defects of submicron scale. The strong field dependences of the activation energy in both regions suggest that artificial pinning centers are needed to enhance the pinning for practical applications. Moreover, the field and current density dependences of the activation energy at relatively high fields are determined as U(J, Hdc )∝J -0.26 H -1.2.

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