arXiv subjects

Jeremy G. Philbrick

Publications and source records attributed to Jeremy G. Philbrick.

6 recordsLinked to original sources

arXiv2026

Layered CrGe1-xSe3+y with Cr Kagome Lattice and Antiferromagnetic Ordering

We report the synthesis and properties of a new layered material, CrGe1-xSe3+y. The crystal structure was determined by using single crystal x-ray diffraction and transmission electron microscopy. CrGe1-xSe3+y crystallizes with a space group R-3m, featuring a double Kagome layer of chromium atoms, sandwiched between disordered Ge-Se layers. This compound displays antiferromagnetic order below 50 K, unlike the ferromagnetic behavior in CrGeTe3. Chromium displays an effective moment of ~3.9 μB/Cr, consistent with Cr3+ oxidation. The presence of this phase limits the possibility of a ferromagnetic CrGeSe3 analogous to CrGeTe3.

cond-mat.mtrl-sci↗

arXiv2024

Absence of Long-Range Magnetic Ordering in a Trirutile High-Entropy Oxide (Mn$_{0.2}$Fe$_{0.2}$Co$_{0.2}$Ni$_{0.2}$Cu$_{0.2}$)Ta$_{1.92}$O$_{6-δ}$

Functionalities of solid-state materials are usually considered to be dependent on their crystal structures. The limited structural types observed in the emerged high-entropy oxides put constraints on exploration of their physical properties and potential applications. Herein, we synthesized the first high-entropy oxide in a trirutile structure, (Mn$_{0.2}$Fe$_{0.2}$Co$_{0.2}$Ni$_{0.2}$Cu$_{0.2}$)Ta$_{1.92}$O$_{6-δ}$, and investigated its magnetism. The phase purity and high-entropy nature were confirmed by powder X-ray diffraction and energy-dispersive spectroscopy, respectively. X-ray photoelectron spectroscopy indicated divalent Mn, Co, Ni and Cu along with trivalent Fe. Magnetic properties measurements showed antiferromagnetic coupling and potential short-range magnetic ordering below ~ 4 K. The temperature-dependent heat capacity data measured under zero and high magnetic field confirmed the lack of long-range magnetic ordering and a possible low-temperature phonon excitation. The discovery of the first trirutile high-entropy oxide opens a new way for studying the relationship between the highly disordered atomic arrangement and their magnetic interaction. Furthermore, it provides a new direction for exploring functionalities of high-entropy oxides.

cond-mat.mtrl-sci↗

arXiv2024

UOTe: Kondo-interacting topological antiferromagnet in a van der Waals lattice

Since the initial discovery of two-dimensional van der Waals (vdW) materials, significant effort has been made to incorporate the three properties of magnetism, band structure topology, and strong electron correlations $-$ to leverage emergent quantum phenomena and expand their potential applications. However, the discovery of a single vdW material that intrinsically hosts all three ingredients has remained an outstanding challenge. Here we report the discovery of a Kondo-interacting topological antiferromagnet in the vdW 5$f$ electron system UOTe. It has a high antiferromagnetic (AFM) transition temperature of 150 K, with a unique AFM configuration that breaks the combined parity and time reversal ($PT$) symmetry in an even number of layers while maintaining zero net magnetic moment. Our angle-resolved photoemission spectroscopy (ARPES) measurements reveal Dirac bands near the Fermi level, which combined with our theoretical calculations demonstrate UOTe as an AFM Dirac semimetal. Within the AFM order, we observed the presence of the Kondo interaction, as evidenced by the emergence of a 5$f$ flat band near the Fermi level below 100 K and hybridization between the Kondo band and the Dirac band. Our density functional theory calculations in its bilayer form predict UOTe as a rare example of a fully-compensated AFM Chern insulator.

cond-mat.str-el↗

arXiv2024

Evolution of Ferromagnetism and Electrical Resistivity in Sb-Doped Cr4PtGa17

We describe the doping effects on a metallic breathing pyrochlore compound, Cr4PtGa17. Upon doping with Sb, i.e., Cr4Pt(Ga1-xSbx)17, it was found that a selective doping on one of the seven Ga sites occurs. With increasing dopant level, the ferromagnetism in the parent compound is gradually suppressed, along with a decrease in fitted Curie-Weiss temperature (from 61 (1) K to -1.8 (1) K) and effective moment (from ~2.26 muB/f.u. to ~0.68 muB/f.u.). Low-temperature heat capacity measurements confirm the absence of magnetic ordering above 0.4 K for the three most doped samples. Meanwhile, electrical resistivity measurements display a metal-semiconductor transition with increasing Sb contents, which is attributed to an increase of Fermi energy based on the calculations of electronic band structure and density of states. Moreover, we have speculated that the ferromagnetism in Cr4PtGa17 is governed by itinerant electrons according to our observations. This study of Sb-doping effect on Cr4PtGa17 provides deeper understanding of magnetism of this system and possibilities for future modifications.

cond-mat.mtrl-sci↗

arXiv2023

Ultra-broadband bright light emission from a one-dimensional inorganic van der Waals material

One-dimensional (1D) van der Waals materials have emerged as an intriguing playground to explore novel electronic and optical effects. We report on inorganic one-dimensional SbPS4 nanotubes bundles obtained via mechanical exfoliation from bulk crystals. The ability to mechanically exfoliate SbPS4 nanobundles offers the possibility of applying modern 2D material fabrication techniques to create mixed-dimensional van der Waals heterostructures. We find that SbPS4 can readily be exfoliated to yield long (> 10 μm) nanobundles with thicknesses that range from of 1.3 - 200 nm. We investigated the optical response of semiconducting SbPS4 nanobundles and discovered that upon excitation with blue light, they emit bright and ultra-broadband red light with a quantum yield similar to that of hBN-encapsulated MoSe2. We discovered that the ultra-broadband red light emission is a result of a large ~1 eV exciton binding energy and a ~200 meV exciton self-trapping energy, unprecedented in previous material studies. Due to the bright and ultra-broadband light emission, we believe that this class of inorganic 1D van der Waals semiconductors has numerous potential applications including on-chip tunable nanolasers, and applications that require ultra-violet to visible light conversion such as lighting and sensing. Overall, our findings open avenues for harnessing the unique characteristics of these nanomaterials, advancing both fundamental research and practical optoelectronic applications.

cond-mat.mtrl-sci↗

arXiv2023

Magnetic Order in A Quenched-High-Temperature-Phase of Cu-Doped MnBi

Permanent magnets are of great importance due to their vast applications. MnBi has been proposed to be a potential permanent magnet that can be widely used while past efforts have been focused on optimizing the ferromagnetic low-temperature phase of MnBi. Herein, we report a series of new materials, CuxMn1-xBi, crystallizing in a quenched high-temperature-phase (QHTP) MnBi-related structure. We synthesized single crystals of CuxMn1-xBi and found that they crystallize in an unreported trigonal structure (P -31c). Magnetic properties measurements imply high-temperature antiferromagnetic (AFM) ordering and low-temperature ferromagnetic or ferrimagnetic (FM/FiM) ordering. By analyzing the doping effect on crystal structure and magnetic properties, we established a magnetic phase diagram for Cu-doped MnBi and attributed the AFM and FM/FiM to two different atomic sites of Mn.

cond-mat.mtrl-sci↗