Jaime A. Fernandez-Baca

Oak Ridge National Laboratory

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Jaime A. Fernandez-Baca has a total of 483 co-authors. Here are the top co-authors by number of shared publications:

Feng Ye
Oak Ridge National Laboratory
30 shared publications
Songxue Chi
Oak Ridge National Laboratory
20 shared publications
J. W. Lynn
NIST Center for Neutron Research, Gaithersburg, Maryland, 20899, USA
13 shared publications
Pengcheng Dai
Department of Physics and Astronomy, The University of Tennessee, Knoxville, Tennessee 37996, USA
13 shared publications
Y. Tokura
ERATO Spin Superstructure Project and Multiferroics Project, JST, Tokyo 113-8656, Japan
13 shared publications
C. W. Chu
Department of Physics and TcSUH, University of Houston, Houston, Texas 77204, USA
10 shared publications

Latest Publications

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Cited by 5
- 15 May 2025
- Published by Physical Society of Japan in Journal of the Physical Society of Japan
Neutron Spectroscopy Study on Crystalline Electric Field Excitations in NdB₄
by Hiroki Yamauchi, Naoto Metoki, Ryuta Watanuki, Tao Hong, Jaime A. Fernandez-Baca, Masato Hagihala, Takatsugu Masuda, Hideki Yoshizawa, Shinichi Itoh
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- 15 May 2025
- Published by Physical Society of Japan in Journal of the Physical Society of Japan
Neutron Spectroscopy Study on Crystalline Electric Field Excitations in NdB₄
by Hiroki Yamauchi, Naoto Metoki, Ryuta Watanuki, Tao Hong, Jaime A. Fernandez-Baca, Masato Hagihala, Takatsugu Masuda, Hideki Yoshizawa, Shinichi Itoh
Cited by 5
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Cited by 2
- 8 August 2024
- Published by American Physical Society (APS) in Physical Review B
Linking ${NH}_{4}^{+}$ motion to magnetism in molecular multiferroic ${({NH}_{4})}_{2} [{FeCl}_{5} (H_{2} O)]$ : A neutron vibrational spectroscopy study
by W. Tian, L. L. Daemen, Y. Q. Cheng, Fei Li, Jaime A. Fernandez-Baca
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- 8 August 2024
- Published by American Physical Society (APS) in Physical Review B
Linking ${NH}_{4}^{+}$ motion to magnetism in molecular multiferroic ${({NH}_{4})}_{2} [{FeCl}_{5} (H_{2} O)]$ : A neutron vibrational spectroscopy study
by W. Tian, L. L. Daemen, Y. Q. Cheng, Fei Li, Jaime A. Fernandez-Baca
Cited by 2
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Cited by 3
- 14 May 2024
- Published by Elsevier in Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment
Incident beamline design for a modern cold triple axis spectrometer at the High Flux Isotope Reactor
by G.E. Granroth, M. Daum, A.A. Aczel, T.J. Williams, B. Winn, J.A. Fernandez-Baca, M. Mourigal, Lumsden
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- 14 May 2024
- Published by Elsevier in Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment
Incident beamline design for a modern cold triple axis spectrometer at the High Flux Isotope Reactor
by G.E. Granroth, M. Daum, A.A. Aczel, T.J. Williams, B. Winn, J.A. Fernandez-Baca, M. Mourigal, Lumsden
Cited by 3
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Cited by 27
- 25 August 2023
- Published by Springer Nature in Nature Communications
Topology stabilized fluctuations in a magnetic nodal semimetal
by Nathan C. Drucker, Thanh Nguyen, Fei Han, Phum Siriviboon, Xi Luo, Nina Andrejevic, Ziming Zhu, Grigory Bednik, Quynh T. Nguyen, Zhantao Chen, et al.
The interplay between magnetism and electronic band topology enriches topological phases and has promising applications. However, the role of topology in magnetic fluctuations has been elusive. Here, we report evidence for topology stabilized magnetism above the magnetic transition temperature in magnetic Weyl semimetal candidate CeAlGe. Electrical transport, thermal transport, resonant elastic X-ray scattering, and dilatometry consistently indicate the presence of locally correlated magnetism within a narrow temperature window well above the thermodynamic magnetic transition temperature. The wavevector of this short-range order is consistent with the nesting condition of topological Weyl nodes, suggesting that it arises from the interaction between magnetic fluctuations and the emergent Weyl fermions. Effective field theory shows that this topology stabilized order is wavevector dependent and can be stabilized when the interband Weyl fermion scattering is dominant. Our work highlights the role of electronic band topology in stabilizing magnetic order even in the classically disordered regime.
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- 25 August 2023
- Published by Springer Nature in Nature Communications
Open Access
Topology stabilized fluctuations in a magnetic nodal semimetal
by Nathan C. Drucker, Thanh Nguyen, Fei Han, Phum Siriviboon, Xi Luo, Nina Andrejevic, Ziming Zhu, Grigory Bednik, Quynh T. Nguyen, Zhantao Chen, et al.
The interplay between magnetism and electronic band topology enriches topological phases and has promising applications. However, the role of topology in magnetic fluctuations has been elusive. Here, we report evidence for topology stabilized magnetism above the magnetic transition temperature in magnetic Weyl semimetal candidate CeAlGe. Electrical transport, thermal transport, resonant elastic X-ray scattering, and dilatometry consistently indicate the presence of locally correlated magnetism within a narrow temperature window well above the thermodynamic magnetic transition temperature. The wavevector of this short-range order is consistent with the nesting condition of topological Weyl nodes, suggesting that it arises from the interaction between magnetic fluctuations and the emergent Weyl fermions. Effective field theory shows that this topology stabilized order is wavevector dependent and can be stabilized when the interband Weyl fermion scattering is dominant. Our work highlights the role of electronic band topology in stabilizing magnetic order even in the classically disordered regime.
Cited by 27
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Cited by 2
- 27 December 2022
- Published by American Physical Society (APS) in Physical Review B
Magnetic structure and spin dynamics of the quasi-two-dimensional antiferromagnet Zn-doped copper pyrovanadate
by G. Gitgeatpong, Y. Zhao, J. A. Fernandez-Baca, T. Hong, T. J. Sato, P. Piyawongwatthana, K. Nawa, P. Saeaun, K. Matan
Magnetic properties of the antiferromagnet ${Zn}_{x} {Cu}_{2 - x} V_{2} O_{7}$ (ZnCVO) with $x \approx 0.06$ have been thoroughly investigated on powder and single-crystal samples. The crystal structure determination using powder x-ray and neutron diffraction confirms that our ZnCVO samples are isostructural with $β - {Cu}_{2} V_{2} O_{7}$ ( $β$ -CVO) with a small deviation in the lattice parameters. Macroscopic magnetic property measurements also confirm the similarity between the two compounds. The ${Cu}^{2 +}$ spins were found to align along the crystallographic $c$ axis, antiparallel to their nearest neighbors connected by the leading exchange interaction $J_{1}$ . Spin dynamics reveals a typical symmetric spin-wave dispersion with strong interactions in the $b c$ plane and weak interplane coupling. The exchange interaction analysis indicates that the spin network of ZnCVO is topologically consistent with the previous DFT prediction but the values of leading exchange interactions are contradictory. Furthermore, rather than the predicted 2D honeycomb structure, the spin network in ZnCVO could be better described by the anisotropic 2D spin network composed of $J_{1}, J_{5}$ , and $J_{6}$ interactions, four bonds per one spin site, coupled by weak interplane interactions.
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- 27 December 2022
- Published by American Physical Society (APS) in Physical Review B
Magnetic structure and spin dynamics of the quasi-two-dimensional antiferromagnet Zn-doped copper pyrovanadate
by G. Gitgeatpong, Y. Zhao, J. A. Fernandez-Baca, T. Hong, T. J. Sato, P. Piyawongwatthana, K. Nawa, P. Saeaun, K. Matan
Magnetic properties of the antiferromagnet ${Zn}_{x} {Cu}_{2 - x} V_{2} O_{7}$ (ZnCVO) with $x \approx 0.06$ have been thoroughly investigated on powder and single-crystal samples. The crystal structure determination using powder x-ray and neutron diffraction confirms that our ZnCVO samples are isostructural with $β - {Cu}_{2} V_{2} O_{7}$ ( $β$ -CVO) with a small deviation in the lattice parameters. Macroscopic magnetic property measurements also confirm the similarity between the two compounds. The ${Cu}^{2 +}$ spins were found to align along the crystallographic $c$ axis, antiparallel to their nearest neighbors connected by the leading exchange interaction $J_{1}$ . Spin dynamics reveals a typical symmetric spin-wave dispersion with strong interactions in the $b c$ plane and weak interplane coupling. The exchange interaction analysis indicates that the spin network of ZnCVO is topologically consistent with the previous DFT prediction but the values of leading exchange interactions are contradictory. Furthermore, rather than the predicted 2D honeycomb structure, the spin network in ZnCVO could be better described by the anisotropic 2D spin network composed of $J_{1}, J_{5}$ , and $J_{6}$ interactions, four bonds per one spin site, coupled by weak interplane interactions.
Cited by 2
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Cited by 115
- 2 December 2020
- Published by Springer Nature in Nature Communications
Quantized thermoelectric Hall effect induces giant power factor in a topological semimetal
by Fei Han, Nina Andrejevic, Thanh Nguyen, Vladyslav Kozii, Quynh T. Nguyen, Tom Hogan, Zhiwei Ding, Ricardo Pablo-Pedro, Shreya Parjan, Brian Skinner, et al.
Thermoelectrics are promising by directly generating electricity from waste heat. However, (sub-)room-temperature thermoelectrics have been a long-standing challenge due to vanishing electronic entropy at low temperatures. Topological materials offer a new avenue for energy harvesting applications. Recent theories predicted that topological semimetals at the quantum limit can lead to a large, non-saturating thermopower and a quantized thermoelectric Hall conductivity approaching a universal value. Here, we experimentally demonstrate the non-saturating thermopower and quantized thermoelectric Hall effect in the topological Weyl semimetal (WSM) tantalum phosphide (TaP). An ultrahigh longitudinal thermopower $$S_{xx} \sim 1.1 \times 10^3 \, \mu \, {\mathrm{V}} \, {\mathrm{K}}^{ - 1}$$ $S_{x x} ~ 1.1 \times 1 0^{3} μ V K^{- 1}$ and giant power factor $$\sim 525 \, \mu \, {\mathrm{W}} \, {\mathrm{cm}}^{ - 1} \, {\mathrm{K}}^{ - 2}$$ $~ 525 μ W {cm}^{- 1} K^{- 2}$ are observed at ~40 K, which is largely attributed to the quantized thermoelectric Hall effect. Our work highlights the unique quantized thermoelectric Hall effect realized in a WSM toward low-temperature energy harvesting applications.
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- 2 December 2020
- Published by Springer Nature in Nature Communications
Open Access
Quantized thermoelectric Hall effect induces giant power factor in a topological semimetal
by Fei Han, Nina Andrejevic, Thanh Nguyen, Vladyslav Kozii, Quynh T. Nguyen, Tom Hogan, Zhiwei Ding, Ricardo Pablo-Pedro, Shreya Parjan, Brian Skinner, et al.
Thermoelectrics are promising by directly generating electricity from waste heat. However, (sub-)room-temperature thermoelectrics have been a long-standing challenge due to vanishing electronic entropy at low temperatures. Topological materials offer a new avenue for energy harvesting applications. Recent theories predicted that topological semimetals at the quantum limit can lead to a large, non-saturating thermopower and a quantized thermoelectric Hall conductivity approaching a universal value. Here, we experimentally demonstrate the non-saturating thermopower and quantized thermoelectric Hall effect in the topological Weyl semimetal (WSM) tantalum phosphide (TaP). An ultrahigh longitudinal thermopower $$S_{xx} \sim 1.1 \times 10^3 \, \mu \, {\mathrm{V}} \, {\mathrm{K}}^{ - 1}$$ $S_{x x} ~ 1.1 \times 1 0^{3} μ V K^{- 1}$ and giant power factor $$\sim 525 \, \mu \, {\mathrm{W}} \, {\mathrm{cm}}^{ - 1} \, {\mathrm{K}}^{ - 2}$$ $~ 525 μ W {cm}^{- 1} K^{- 2}$ are observed at ~40 K, which is largely attributed to the quantized thermoelectric Hall effect. Our work highlights the unique quantized thermoelectric Hall effect realized in a WSM toward low-temperature energy harvesting applications.
Cited by 115
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Cited by 13
- 25 August 2020
- Published by American Physical Society (APS) in Physical Review B
Evolution of the structural transition in ${Mo}_{1 - x} W_{x} {Te}_{2}$
by John A. Schneeloch, Yu Tao, Chunruo Duan, Masaaki Matsuda, Adam A. Aczel, Jaime A. Fernandez-Baca, Guangyong Xu, Jörg C. Neuefeind, Junjie Yang, Despina Louca
The composition dependence of the structural transition between the monoclinic $1 T^{'}$ and orthorhombic $T_{d}$ phases in the ${Mo}_{1 - x} W_{x} {Te}_{2}$ Weyl semimetal was investigated by elastic neutron scattering on single crystals up to $x \approx 0.54$ . First observed in ${MoTe}_{2}$ , the transition from $T_{d}$ to $1 T^{'}$ is accompanied by an intermediate pseudo-orthorhombic phase, $T_{d}^{*}$ . Upon doping with W, the $T_{d}^{*}$ phase vanishes by $x \approx 0.34$ . Above this concentration, a phase coexistence behavior with both $T_{d}$ and $1 T^{'}$ is observed instead. The interlayer in-plane positioning parameter $δ$ , which relates to the $1 T^{'} β$ angle, decreases with temperature as well as with W substitution, likely due to strong anharmonicity in the interlayer interactions. The temperature width of the phase coexistence remains almost constant up to $x \approx 0.54$ , in contrast to the broadening reported under pressure.
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- 25 August 2020
- Published by American Physical Society (APS) in Physical Review B
Evolution of the structural transition in ${Mo}_{1 - x} W_{x} {Te}_{2}$
by John A. Schneeloch, Yu Tao, Chunruo Duan, Masaaki Matsuda, Adam A. Aczel, Jaime A. Fernandez-Baca, Guangyong Xu, Jörg C. Neuefeind, Junjie Yang, Despina Louca
The composition dependence of the structural transition between the monoclinic $1 T^{'}$ and orthorhombic $T_{d}$ phases in the ${Mo}_{1 - x} W_{x} {Te}_{2}$ Weyl semimetal was investigated by elastic neutron scattering on single crystals up to $x \approx 0.54$ . First observed in ${MoTe}_{2}$ , the transition from $T_{d}$ to $1 T^{'}$ is accompanied by an intermediate pseudo-orthorhombic phase, $T_{d}^{*}$ . Upon doping with W, the $T_{d}^{*}$ phase vanishes by $x \approx 0.34$ . Above this concentration, a phase coexistence behavior with both $T_{d}$ and $1 T^{'}$ is observed instead. The interlayer in-plane positioning parameter $δ$ , which relates to the $1 T^{'} β$ angle, decreases with temperature as well as with W substitution, likely due to strong anharmonicity in the interlayer interactions. The temperature width of the phase coexistence remains almost constant up to $x \approx 0.54$ , in contrast to the broadening reported under pressure.
Cited by 13
Open Access
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Cited by 6
- 29 July 2020
- Published by American Physical Society (APS) in Physical Review B
Competition of three-dimensional magnetic phases in ${Ca}_{2} {Ru}_{1 - x} {Fe}_{x} O_{4}$ : A structural perspective
by Songxue Chi, Feng Ye, Gang Cao, Huibo Cao, Jaime A. Fernandez-Baca
The crystalline and magnetic structures of ${Ca}_{2} {Ru}_{1 - x} {Fe}_{x} O_{4}$ ( $x = 0.02$ , 0.05, 0.08, and 0.12) have been studied using neutron and x-ray diffraction. The Fe-doping reduces the Ru-O bond length in both apical and planar directions. The smaller Ru( $Fe) O_{6}$ octahedron leads to its reduced distortion. The $P b c a$ space group is maintained in all the Fe dopings, so is the octahedral flattening. Warming has a similar effect on the lattice to that of the Fe doping in releasing the distorted octahedra but precipitates an abrupt octahedral elongation near the $N \overset{́}{e} el$ temperature. Two competing antiferromagnetic orders, $A$ - and $B$ -centered phases have been observed. The Fe-doping-relaxed crystal structure prefers the latter to the former. As the doping increases, the $B$ -centered phase continuously grows at the cost of the $A$ -centered one and eventually replaces it at $x = 0.12$ . The absence of the two-dimensional antiferromagnetic critical fluctuations above the magnetic transition temperature and the three-dimensional magnetic correlation below the transition, together with the anomalous lattice response, point to an important role of orbital degree of freedom in driving the magnetic phase competition.
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- 29 July 2020
- Published by American Physical Society (APS) in Physical Review B
Open Access
Competition of three-dimensional magnetic phases in ${Ca}_{2} {Ru}_{1 - x} {Fe}_{x} O_{4}$ : A structural perspective
by Songxue Chi, Feng Ye, Gang Cao, Huibo Cao, Jaime A. Fernandez-Baca
The crystalline and magnetic structures of ${Ca}_{2} {Ru}_{1 - x} {Fe}_{x} O_{4}$ ( $x = 0.02$ , 0.05, 0.08, and 0.12) have been studied using neutron and x-ray diffraction. The Fe-doping reduces the Ru-O bond length in both apical and planar directions. The smaller Ru( $Fe) O_{6}$ octahedron leads to its reduced distortion. The $P b c a$ space group is maintained in all the Fe dopings, so is the octahedral flattening. Warming has a similar effect on the lattice to that of the Fe doping in releasing the distorted octahedra but precipitates an abrupt octahedral elongation near the $N \overset{́}{e} el$ temperature. Two competing antiferromagnetic orders, $A$ - and $B$ -centered phases have been observed. The Fe-doping-relaxed crystal structure prefers the latter to the former. As the doping increases, the $B$ -centered phase continuously grows at the cost of the $A$ -centered one and eventually replaces it at $x = 0.12$ . The absence of the two-dimensional antiferromagnetic critical fluctuations above the magnetic transition temperature and the three-dimensional magnetic correlation below the transition, together with the anomalous lattice response, point to an important role of orbital degree of freedom in driving the magnetic phase competition.
Cited by 6
Open Access
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Cited by 23
- 21 July 2020
- Published by Springer Nature in Communications Materials
High-temperature short-range order in Mn3RhSi
by Hiroki Yamauchi, Dita Puspita Sari, Isao Watanabe, Yukio Yasui, Lieh-Jeng Chang, Keietsu Kondo, Takashi U. Ito, Motoyuki Ishikado, Masato Hagihara, Matthias D. Frontzek, et al.
Conventional phase transitions are well understood in terms of the order parameter, based on the Landau–Ginzburg–Wilson theory. However, unconventional magnetic orders have been observed in clean systems such as MnSi. The unconventional magnetic orders of conduction electrons in the metallic phase has been observed for high-temperature superconductors and heavy fermion compounds. However, these unconventional magnetic orders have been limited to relatively low temperatures as quantum phase transitions. Here high-temperature magnetic short-range order is observed as one of the unconventional magnetic orders at temperatures up to 720 K in a noncentrosymmetric intermetallic antiferromagnet Mn₃RhSi with a well-ordered lattice. The magnetic Mn ions form a hyperkagome network of corner-sharing triangles, where the spins are geometrically frustrated. The spin network is equivalent to that of a spin liquid and non-Fermi-liquid material, β-Mn. Our observation indicates that a metallic phase with magnetic short-range order exists at high temperatures.
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- 21 July 2020
- Published by Springer Nature in Communications Materials
Open Access
High-temperature short-range order in Mn3RhSi
by Hiroki Yamauchi, Dita Puspita Sari, Isao Watanabe, Yukio Yasui, Lieh-Jeng Chang, Keietsu Kondo, Takashi U. Ito, Motoyuki Ishikado, Masato Hagihara, Matthias D. Frontzek, et al.
Conventional phase transitions are well understood in terms of the order parameter, based on the Landau–Ginzburg–Wilson theory. However, unconventional magnetic orders have been observed in clean systems such as MnSi. The unconventional magnetic orders of conduction electrons in the metallic phase has been observed for high-temperature superconductors and heavy fermion compounds. However, these unconventional magnetic orders have been limited to relatively low temperatures as quantum phase transitions. Here high-temperature magnetic short-range order is observed as one of the unconventional magnetic orders at temperatures up to 720 K in a noncentrosymmetric intermetallic antiferromagnet Mn₃RhSi with a well-ordered lattice. The magnetic Mn ions form a hyperkagome network of corner-sharing triangles, where the spins are geometrically frustrated. The spin network is equivalent to that of a spin liquid and non-Fermi-liquid material, β-Mn. Our observation indicates that a metallic phase with magnetic short-range order exists at high temperatures.
Cited by 23
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Cited by 14
- 12 August 2019
- Published by Springer Nature in npj Quantum Materials
Magnetic field-temperature phase diagram of multiferroic (NH4)2FeCl5·H2O
by Amanda J. Clune, Jisoo Nam, Minseong Lee, Kendall D. Hughey, Wei Tian, Jaime A. Fernandez-Baca, Randy S. Fishman, John Singleton, Jun Hee Lee, Janice L. Musfeldt
Owing to their overall low energy scales, flexible molecular architectures, and ease of chemical substitution, molecule-based multiferroics are extraordinarily responsive to external stimuli and exhibit remarkably rich phase diagrams. Even so, the stability and microscopic properties of various magnetic states in close proximity to quantum critical points are highly under-explored in these materials. Inspired by these opportunities, we combined pulsed-field magnetization, first-principles calculations, and numerical simulations to reveal the magnetic field–temperature (B–T) phase diagram of multiferroic (NH₄)₂FeCl₅⋅H₂O. In this system, a network of intermolecular hydrogen and halogen bonds creates a competing set of exchange interactions that generates additional structure in the phase diagram—both in the vicinity of the spin flop and near the 30 T transition to the fully saturated state. Consequently, the phase diagrams of (NH₄)₂FeCl₅⋅H₂O and its deuterated analog are much more complex than those of other molecule-based multiferroics. The entire series of coupled electric and magnetic transitions can be accessed with a powered magnet, opening the door to exploration and control of properties in this and related materials.
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- 12 August 2019
- Published by Springer Nature in npj Quantum Materials
Open Access
Magnetic field-temperature phase diagram of multiferroic (NH4)2FeCl5·H2O
by Amanda J. Clune, Jisoo Nam, Minseong Lee, Kendall D. Hughey, Wei Tian, Jaime A. Fernandez-Baca, Randy S. Fishman, John Singleton, Jun Hee Lee, Janice L. Musfeldt
Owing to their overall low energy scales, flexible molecular architectures, and ease of chemical substitution, molecule-based multiferroics are extraordinarily responsive to external stimuli and exhibit remarkably rich phase diagrams. Even so, the stability and microscopic properties of various magnetic states in close proximity to quantum critical points are highly under-explored in these materials. Inspired by these opportunities, we combined pulsed-field magnetization, first-principles calculations, and numerical simulations to reveal the magnetic field–temperature (B–T) phase diagram of multiferroic (NH₄)₂FeCl₅⋅H₂O. In this system, a network of intermolecular hydrogen and halogen bonds creates a competing set of exchange interactions that generates additional structure in the phase diagram—both in the vicinity of the spin flop and near the 30 T transition to the fully saturated state. Consequently, the phase diagrams of (NH₄)₂FeCl₅⋅H₂O and its deuterated analog are much more complex than those of other molecule-based multiferroics. The entire series of coupled electric and magnetic transitions can be accessed with a powered magnet, opening the door to exploration and control of properties in this and related materials.
Cited by 14

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