Two-dimensional (2D) materials are promising candidates for next-generation electronic devices. In this regime, insulating 2D ferromagnets, which remain rare, are of special importance due to their potential for enabling new device architectures. Here we report the discovery of ferromagnetism in a layered van der Waals semiconductor, VI 3 , which is based on honeycomb vanadium layers separated by an iodine-iodine van der Waals gap. It has a BiI 3 -type structure (R-3, No.148) at room temperature, and our experimental evidence suggests that it may undergo a subtle structural phase transition at 78 K. VI 3 becomes ferromagnetic at 49 K, below which magneto-optical Kerr effect imaging clearly shows ferromagnetic domains, which can be manipulated by the applied external magnetic field. The optical band gap determined by reflectance measurements is 0.6 eV, and the material is highly resistive.

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Previously unreported High-Entropy Alloy (HEA) superconductors in the pentanary (ZrNb)1−x[MoReRu]x, (HfTaWIr)1−x[Re]x, and (HfTaWPt)1−x[Re]x systems are described and characterized.

We have synthesized previously unreported high-entropy alloys (HEAs) in the pentanary (ScZrNb)1–x [RhPd] x and hexanary (ScZrNbTa)1–x [RhPd] x systems. The materials have CsCl-type structures and mixed site occupancies. Both HEAs are type-II superconductors with strongly varying critical temperatures (T c’s) depending on the valence electron count (VEC); the T c’s increase monotonically with decreasing VEC within each series, and do not follow the trends seen for either crystalline or amorphous transition metal superconductors. The (ScZrNb)0.65[RhPd]0.35 HEA with the highest T c, ∼9.3 K, also exhibits the largest μ0 H c2(0) = 10.7 T. The pentanary and hexanary HEAs have higher superconducting transition temperatures than their simple binary intermetallic relatives with the CsCl-type structure and a surprisingly ductile mechanical behavior. The presence of niobium, even at the 20% level, has a positive impact on the T c. Nevertheless, niobium-free (ScZr)0.50[RhPd]0.50, as mother-compound of both superconducting HEAs found here, is itself superconducting, proving that superconductivity is an intrinsic feature of the bulk material.

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