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The relatively low Curie temperature (Tc) in recently discovered two-dimensional ferromagnetic (FM) materials has limited their potential applications in designing next generation electronics. Searching for new low-dimensional layered materials with room-temperature Tc is highly needed. Here, we report the study of layered FM materials Cr5+xTe8 (x = −0.10, 0.11, 0.56, 1) in which Tc can be well manipulated by the Cr content. Single crystalline Cr5+xTe8 samples have been synthesized and characterized by energy dispersive x-ray spectroscopy, x-ray diffraction, and magnetization measurements. We have found that Tc increases monotonically with Cr content and reaches 313 K at x = 1. While the FM coupling is enhanced with an increase in the Cr content, the antiferromagnetic (AFM) phase at low temperatures is suppressed. Due to the competition of FM and AFM phases, a wasp-waist loop is observed on isothermal magnetization curves. A magnetic flip occurs by changing the temperature and magnetic field to overcome the flipping energy barrier. Our results indicate that the Cr5+xTe8 system serves as a promising platform to tune the 2D ferromagnetism in layered materials.

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Z-type hexaferrites Ba3(Zn1−xCox)2Fe24O41 (x = 0.2, 0.4, 0.6, 0.8, defined as Z1–Z4) were synthesized by a sol–gel method.

Introducing artificial antidots into superconductors is an efficient way to improve the superconducting properties for application. However, besides the pioneering theoretical studies, the fundamental question concerning how many vortices can be trapped by the antidot still needs to be further clarified from an experimental point of view. In this study, by the e-beam lithography, antidots with different sizes and shapes are fabricated in a superconducting Pb film. The vortex distribution at antidots has been directly imaged using the low-temperature scanning Hall probe microscope. A universal scaling behavior is found that the number of trapped vortices mainly depends on the size of the antidots, irrespective of the shape of antidots. The results shed light on the study of vortex pinning at artificial pinning centers, which is important for practical applications.

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Flux quantization has been widely regarded as the hallmark of the macroscopic quantum state of superconductivity. However, practical design of superconductor devices exploiting finite size confinement effects may induce exotic phenomena, including nonquantized vortices. In our research, the magnetic flux of vortices has been studied in a series of superconducting strips as a function of the strip width and the penetration depth. In both circumstances, the observation using scanning Hall probe microscope (SHPM) displays a controlled evolution from singly quantized vortices to nonquantized ones. It is also found that the magnetic flux is immune to the flowing supercurrent. The simulations based on Ginzburg−Landau theory agree well with experimental results. The observed behavior of the vortex flux may open new perspectives for fundamental research and applications based on vortex matter, such as vortex-memory devices and magnetic field traps for ultracold atoms.

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.