Andrew Treglia
Current Organizations / Institutes
The organizations/institutes from the scholar's latest article
Research Subjects
Andrew Treglia has a total of 22 co-authors. Here are the top co-authors by number of shared publications:
- Rebecca W. Smaha
National Laboratory of the Rockies
2 shared publications - Sage R. Bauers
Materials Sciences Center National Renewable Energy Laboratory 80401 Golden Colorado United States
2 shared publications - Andriy Zakutayev
National Laboratory of the Rockies Golden Colorado USA
1 shared publication - Baptiste Julien
Materials Science Center
1 shared publication - Brian M. Wieliczka
Clarendon Laboratory, Department of Physics
1 shared publication - Brian Skinner
Ohio State University
1 shared publication
Latest Publications
- 11 July 2025
- Published by American Physical Society (APS) in Physical Review B
- Vol. 112 (3) , 035135
Refining the two-band model for highly compensated semimetals using thermoelectric coefficients
In studying compensated semimetals, the two-band model has proven extremely useful in capturing electrical conductivity under magnetic field, as a function of density and mobility of electronlike and holelike carriers. However, it rarely offers practical insight into magnetothermoelectric properties. Here, we report the field dependence of thermoelectric (TE) coefficients in a highly compensated semimetal ${\mathrm{NbSb}}_{2}$, where we find the Seebeck (${S}_{xx}$) and Nernst (${S}_{xy}$) coefficients increase quadratically and linearly with applied magnetic field, respectively. Such field dependence was predicted in previous work that studied a system of two parabolic bands, within semiclassical Boltzmann transport theory when the following two conditions are simultaneously met: ${\ensuremath{\omega}}_{c}\ensuremath{\tau}\ensuremath{\gg}1$ and $tan{\ensuremath{\theta}}_{H}\ensuremath{\ll}1$, where ${\ensuremath{\omega}}_{c}$ and $\ensuremath{\tau}$ refer to the cyclotron frequency and relaxation time, respectively, and ${\ensuremath{\theta}}_{H}$ is the Hall angle. Under these conditions, we find the field dependence of the TE coefficients directly provides a relation between the electronlike (${n}_{e}$) and holelike (${n}_{h}$) carrier densities, which in turn can be used to refine two-band model fitting. With this, we find the compensation factor ($\frac{|\mathrm{\ensuremath{\Delta}}n|}{{n}_{e}}$, where $\mathrm{\ensuremath{\Delta}}n={n}_{e}\ensuremath{-}{n}_{h}$) of ${\mathrm{NbSb}}_{2}$ is two orders of magnitude smaller than what was found in unrestricted fitting, resulting in a larger saturation-field scale for magnetoresistance. Within the same framework of the semiclassical theory, we also deduce that the thermoelectric Hall angle $tan{\ensuremath{\theta}}_{\ensuremath{\gamma}}=\frac{{S}_{xy}}{{S}_{xx}}$ can be expressed as $(\frac{\mathrm{\ensuremath{\Delta}}n}{{n}_{e}}\ifmmode\times\else\texttimes\fi{}{\ensuremath{\omega}}_{c}\ensuremath{\tau}{)}^{\ensuremath{-}1}$, which serves as a parameter to predict the degree of compensation. Our findings offer crucial insights into identifying empirical conditions for field-induced enhancement of TE performance and into engineering-efficient thermoelectric devices based on semimetallic materials.- 11 July 2025
- Published by American Physical Society (APS) in Physical Review B
- Vol. 112 (3) , 035135
Refining the two-band model for highly compensated semimetals using thermoelectric coefficients
In studying compensated semimetals, the two-band model has proven extremely useful in capturing electrical conductivity under magnetic field, as a function of density and mobility of electronlike and holelike carriers. However, it rarely offers practical insight into magnetothermoelectric properties. Here, we report the field dependence of thermoelectric (TE) coefficients in a highly compensated semimetal ${\mathrm{NbSb}}_{2}$, where we find the Seebeck (${S}_{xx}$) and Nernst (${S}_{xy}$) coefficients increase quadratically and linearly with applied magnetic field, respectively. Such field dependence was predicted in previous work that studied a system of two parabolic bands, within semiclassical Boltzmann transport theory when the following two conditions are simultaneously met: ${\ensuremath{\omega}}_{c}\ensuremath{\tau}\ensuremath{\gg}1$ and $tan{\ensuremath{\theta}}_{H}\ensuremath{\ll}1$, where ${\ensuremath{\omega}}_{c}$ and $\ensuremath{\tau}$ refer to the cyclotron frequency and relaxation time, respectively, and ${\ensuremath{\theta}}_{H}$ is the Hall angle. Under these conditions, we find the field dependence of the TE coefficients directly provides a relation between the electronlike (${n}_{e}$) and holelike (${n}_{h}$) carrier densities, which in turn can be used to refine two-band model fitting. With this, we find the compensation factor ($\frac{|\mathrm{\ensuremath{\Delta}}n|}{{n}_{e}}$, where $\mathrm{\ensuremath{\Delta}}n={n}_{e}\ensuremath{-}{n}_{h}$) of ${\mathrm{NbSb}}_{2}$ is two orders of magnitude smaller than what was found in unrestricted fitting, resulting in a larger saturation-field scale for magnetoresistance. Within the same framework of the semiclassical theory, we also deduce that the thermoelectric Hall angle $tan{\ensuremath{\theta}}_{\ensuremath{\gamma}}=\frac{{S}_{xy}}{{S}_{xx}}$ can be expressed as $(\frac{\mathrm{\ensuremath{\Delta}}n}{{n}_{e}}\ifmmode\times\else\texttimes\fi{}{\ensuremath{\omega}}_{c}\ensuremath{\tau}{)}^{\ensuremath{-}1}$, which serves as a parameter to predict the degree of compensation. Our findings offer crucial insights into identifying empirical conditions for field-induced enhancement of TE performance and into engineering-efficient thermoelectric devices based on semimetallic materials.- Open Access
- 24 October 2024
- Published by American Physical Society (APS) in Physical Review Materials
- Vol. 8 (10)
Thin film synthesis, structural analysis, and magnetic properties of novel ternary transition metal nitrideRecent high-throughput computational searches have predicted many novel ternary nitride compounds providing new opportunities for materials discovery in underexplored phase spaces. Nevertheless, there are hardly any predictions and/or syntheses that incorporate only transition metals into new ternary nitrides. Here, we report on the synthesis, structure, and properties of MnCoN 2 , a new ternary nitride material comprising only transition metals and N. We find that crystalline MnCoN 2 can be stabilized over its competing binaries, and over a tendency of this system to become amorphous, by controlling growth temperature within a narrow window slightly above ambient condition. We find that single-phase MnCoN 2 thin films form in a cation-disordered rocksalt crystal structure. X-ray photoelectron spectroscopy analysis suggests that MnCoN 2 is sensitive to oxygen through various oxides and hydroxides binding to cobalt on the surface. X-ray absorption spectroscopy is used to verify that Mn 3 + and Co 3 + cations exist in an octahedrally coordinated environment, which is distinct from a combination of CoN and MnN binaries and in agreement with the rocksalt-based crystal structure prediction. Magnetic measurements suggest that MnCoN 2 has a canted antiferromagnetic ground state below 10 K. We extract a Weiss temperature of θ = − 49.7 K , highlighting the antiferromagnetic correlations in MnCoN 2 . Published by the American Physical Society 2024
- 24 October 2024
- Published by American Physical Society (APS) in Physical Review Materials
- Vol. 8 (10)
Open AccessThin film synthesis, structural analysis, and magnetic properties of novel ternary transition metal nitrideRecent high-throughput computational searches have predicted many novel ternary nitride compounds providing new opportunities for materials discovery in underexplored phase spaces. Nevertheless, there are hardly any predictions and/or syntheses that incorporate only transition metals into new ternary nitrides. Here, we report on the synthesis, structure, and properties of MnCoN 2 , a new ternary nitride material comprising only transition metals and N. We find that crystalline MnCoN 2 can be stabilized over its competing binaries, and over a tendency of this system to become amorphous, by controlling growth temperature within a narrow window slightly above ambient condition. We find that single-phase MnCoN 2 thin films form in a cation-disordered rocksalt crystal structure. X-ray photoelectron spectroscopy analysis suggests that MnCoN 2 is sensitive to oxygen through various oxides and hydroxides binding to cobalt on the surface. X-ray absorption spectroscopy is used to verify that Mn 3 + and Co 3 + cations exist in an octahedrally coordinated environment, which is distinct from a combination of CoN and MnN binaries and in agreement with the rocksalt-based crystal structure prediction. Magnetic measurements suggest that MnCoN 2 has a canted antiferromagnetic ground state below 10 K. We extract a Weiss temperature of θ = − 49.7 K , highlighting the antiferromagnetic correlations in MnCoN 2 . Published by the American Physical Society 2024
- Open Access
- 9 September 2024
- Published by AIP Publishing in Applied Physics Letters
- Vol. 125 (11)
GdWN3 is a nitride perovskite
Nitride perovskites ABN3 are an emerging and highly underexplored class of materials that are of interest due to their intriguing calculated ferroelectric, optoelectronic, and other functional properties. Incorporating novel A-site cations is one strategy to tune and expand such properties; for example, Gd3+ is compelling due to its large magnetic moment, potentially leading to multiferroic behavior. However, the theoretically predicted ground state of GdWN3 was a non-perovskite monoclinic structure. Here, we experimentally show that GdWN3−y crystallizes in a perovskite structure. High-throughput combinatorial sputtering with activated nitrogen is employed to synthesize thin films of Gd2−xWxN3−yOy with oxygen content y < 0.05. Ex situ annealing crystallizes a polycrystalline perovskite phase in a narrow composition window near x = 1. LeBail fits of synchrotron grazing incidence wide angle x-ray scattering data are consistent with a perovskite ground-state structure. Refined density functional theory calculations that included antiferromagnetic configurations confirm that the ground-state structure of GdWN3 is a distorted Pnma perovskite with antiferromagnetic ordering, in contrast to prior predictions. Initial property measurements find that GdWN3−y is paramagnetic down to T = 2 K with antiferromagnetic correlations and that the absorption onset depends on cation stoichiometry. This work provides an important path toward both the rapid expansion of the emerging family of nitride perovskites and understanding their potential multiferroic properties.
- 9 September 2024
- Published by AIP Publishing in Applied Physics Letters
- Vol. 125 (11)
Open AccessGdWN3 is a nitride perovskite
Nitride perovskites ABN3 are an emerging and highly underexplored class of materials that are of interest due to their intriguing calculated ferroelectric, optoelectronic, and other functional properties. Incorporating novel A-site cations is one strategy to tune and expand such properties; for example, Gd3+ is compelling due to its large magnetic moment, potentially leading to multiferroic behavior. However, the theoretically predicted ground state of GdWN3 was a non-perovskite monoclinic structure. Here, we experimentally show that GdWN3−y crystallizes in a perovskite structure. High-throughput combinatorial sputtering with activated nitrogen is employed to synthesize thin films of Gd2−xWxN3−yOy with oxygen content y < 0.05. Ex situ annealing crystallizes a polycrystalline perovskite phase in a narrow composition window near x = 1. LeBail fits of synchrotron grazing incidence wide angle x-ray scattering data are consistent with a perovskite ground-state structure. Refined density functional theory calculations that included antiferromagnetic configurations confirm that the ground-state structure of GdWN3 is a distorted Pnma perovskite with antiferromagnetic ordering, in contrast to prior predictions. Initial property measurements find that GdWN3−y is paramagnetic down to T = 2 K with antiferromagnetic correlations and that the absorption onset depends on cation stoichiometry. This work provides an important path toward both the rapid expansion of the emerging family of nitride perovskites and understanding their potential multiferroic properties.