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Yi, Jieyu

Publications and source records attributed to Yi, Jieyu.

10 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Tuning Magnetic Soliton Phase via Dimensional Confinement in Exfoliated 2D Cr 1/3 NbS 2 Thin Flakes

Thin flakes of Cr 1/3 NbS 2 are fabricated successfully via microexfoliation techniques. Temperature-dependent and field-dependent magnetizations of thin flakes with various thicknesses are investigated. When the thickness of the flake is around several hundred nanometers, the softening and eventual disappearance of the bulk soliton peak is accompanied by the appearance of other magnetic peaks at lower magnetic fields. The emergence and annihilation of the soliton peaks are explained and simulated theoretically by the change in spin spiral number inside the soliton lattice due to dimensional confinement. Compared to the conventional magnetic states in nanoscale materials, the stability and thickness tunability of quantified spin spirals make Cr 1/3 NbS 2 a potential candidate for spintronics nanodevices beyond Moore’s law.

2D materials↗
DOE OSTI2017

Dimensionality Effects in FeGe 2 Nanowires: Enhanced Anisotropic Magnetization and Anomalous Electrical Transport

Here, we report the synthesis of single-crystal iron germanium nanowires via chemical vapor deposition without the assistance of any catalysts. The assembly of single-crystal FeGe 2 nanowires with tetragonal C16 crystal structure shows anisotropic magnetic behavior along the radial direction or the growth axial direction, with both antiferromagnetic and ferromagnetic orders. Single FeGe 2 nanowire devices were fabricated using e-beam lithography. Electronic transport measurement in these devices show two resistivity anomalies near 250 K and 200 K which are likely signatures of the two spin density wave states in FeGe 2 .

36 MATERIALS SCIENCE↗
DOE OSTI2016

Competing antiferromagnetism in a quasi-2D itinerant ferromagnet: Fe 3 GeTe 2

Fe 3 GeTe 2 is known as an air-stable layered metal with itinerant ferromagnetism with a transition temperature of about 220 K. From extensive dc and ac magnetic measurements, we have determined that the ferromagnetic layers of Fe 3 GeTe 2 order antiferromagnetically along the c-axis blow 152 K. The antiferromagnetic state was further substantiated by theoretical calculation to be the ground state. A magnetic structure model was proposed to describe the antiferromagnetic ground state as well as competition between antiferromagnetic and ferromagnetic states. Furthermore, Fe 3 GeTe 2 shares many common features with pnictide superconductors and may be a promising system in which to search for unconventional superconductivity.

2D material↗
DOE OSTI2016

Electronic structure of the chiral helimagnet and 3d-intercalated transition metal dichalcogenide Cr 1/3 NbS 2

The electronic structure of the chiral helimagnet Cr 1/3 NbS 2 has been studied with core level and angle-resolved photoemission spectroscopy (ARPES). Intercalated Cr atoms are found to be effective in donating electrons to the NbS 2 layers but also cause significant modifications of the electronic structure of the host NbS 2 material. Specifically, the data provide evidence that a description of the electronic structure of Cr 1/3 NbS 2 on the basis of a simple rigid band picture is untenable. The data also reveal substantial inconsistencies with the predictions of standard density functional theory. In conclusion, the relevance of these results to the attainment of a correct description of the electronic structure of chiral helimagnets, magnetic thin films/multilayers, and transition metal dichalcogenides intercalated with 3d magnetic elements is discussed.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Ferromagnetism and Nonmetallic Transport of Thin-Film α - FeSi 2 : A Stabilized Metastable Material

The epitaxially stabilized metallic α - FeSi 2 thin films on Si(001) were grown using pulsed laser deposition. While the bulk material of α - FeSi 2 is a high temperature metastable phase and nonmagnetic, the thin film is stabilized at room temperature and shows unusual electronic transport and magnetic properties due to strain modification. The transport renders two different conducting states with a strong crossover at 50 K accompanied by an onset of ferromagnetism as well as a substantial magnetocaloric effect and magnetoresistance. These experimental results are discussed in terms of the unusual electronic structure of α - FeSi 2 obtained within density functional calculations and Boltzmann transport calculations with and without strain. Our findings provide an example of a tailored material with interesting physics properties for practical applications.

36 MATERIALS SCIENCE↗
DOE OSTI2013

Room-Temperature Multiferroic Hexagonal LuFeO3

We observed the coexistence of ferroelectricity and weak ferromagnetism at room temperature in the hexagonal phase of LuFeO3 stabilized by epitaxial thin film growth. While the ferroelectricity in hexagonal LuFeO3 can be understood as arising from its polar structure, the observation of weak ferromagnetism at room temperature is remarkable considering the frustrated triangular spin structure. An explanation of the room temperature weak ferromagnetism is proposed in terms of a subtle lattice distortion revealed by the structural characterization. The combination of ferroelectricity and weak ferromagnetism in epitaxial films at room temperature offers great potential for the application of this novel multiferroic material in next generation devices.

Cheng, Xuemei↗