Enhanced Magnetic Interaction between Ga and Fe in Two-Dimensional van der Waals Ferromagnetic Crystal Fe_(3)GaTe_(2)

Fe_(3)GaTe_(2),a recently discovered van der Waals ferromagnetic crystal with the highest Curie temperature and strong perpendicular magnetic anisotropy among two-dimensional(2D)magnetic materials,has attracted significant attention and makes it a promising candidate for next-generation spintronic applications.Compared with Fe_(3)GeTe_(2),which has the similar crystal structure,the mechanism of the enhanced ferromagnetic properties in Fe_(3)GaTe_(2)is still unclear and needs to be investigated.Here,by using x-ray magnetic circular dichroism measurements,we find that both Ga and Te atoms contribute to the total magnetic moment of the system with antiferromagnetic coupling to Fe atoms.Our first-principles calculations reveal that Fe_(3)GaTe_(2)has van Hove singularities at the Fermi level in nonmagnetic state,resulting in the magnetic instability of the system and susceptibility to magnetic phase transitions.In addition,the calculation results about the density of states in ferromagnetic states of two materials suggest that the exchange interaction between Fe atoms is strengthened by replacing Ge atoms with Ga atoms.These findings indicate the increase of both the itinerate and local moments in Fe_(3)GaTe_(2)in view of Stoner and exchange interaction models,which results in the enhancement of the overall magnetism and a higher Curie temperature.Our work provides insight into the underlying mechanism of Fe_(3)GaTe_(2)’s remarkable magnetic properties and has important implications for searching 2D materials with expected magnetic properties in the future.

Performance of the merged APPLE-Knot undulator for soft x-ray beamline in medium energy ring

APPLE-Knot undulator can effectively solve the on-axis heat load problem and is proven to perform well in VUV beamline and soft x-ray beamline in high energy storage ring. However, for soft x-ray beamline in a medium energy ring,whether the APPLE-Knot undulator excels the APPLE undulator is still a question. Here, a merged APPLE-Knot undulator is studied to generate soft x-ray in a medium energy ring. Its advantages and problems are discussed. Though the on-axis heat load of the APPLE-Knot undulator is lower in linear polarization modes compared to the APPLE undulator, its flux is lower. The APPLE-Knot undulator shows no advantage when only fundamental harmonic is needed. However, in circular polarization mode, the APPLE-Knot undulator shows the ability to cover a broader energy range which can remedy the notable shortcoming of the APPLE undulator.

Anisotropy of Electronic Spin Texture in the High-Temperature Cuprate Superconductor Bi_(2)Sr_(2)CaCu_(2)O_(8+δ)

Seeking new order parameters and the related broken symmetry and studying their relationship with phase transition have been important topics in condensed matter physics.Here,by using spin-and angle-resolved photoemission spectroscopy,we confirm the helical spin texture caused by spin-layer locking in the nodal region in the cuprate superconductor Bi_(2)Sr_(2)CaCu_(2)O_(8+δ)and discover the anisotropy of spin polarizations at nodes alongΓ–X andΓ–Y directions.The breaking of C_(4)rotational symmetry in electronic spin texture may give deeper insights into understanding the ground state of cuprate superconductors.