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Recent Submissions
Second harmonic generation and ferromagnetic resonance of BaTiO3-BiFeO3 films and nanorod arrays
Smith, Nicholas W. G.; Mudiyanselage, Rathsara R. H. H.; Wu, Shuang; Emori, Satoru; Magill, Brenden A.; Priya, Shashank; Khodaparast, Giti A. (IOP Publishing, 2025-07-01)
The solid solution of BaTiO3-BiFeO3 (BTO-BFO) exhibits enhanced magneto-electric coupling compared to the widely explored BiFeO3. In this study, we examined BTO-BFO nanorod arrays (and films) ranging from 200 to 600 nm in height (and thickness) by employing second harmonic emission (SHE) and ferromagnetic resonance (FMR) measurements. We demonstrated a large enhancement in SHE in nanorod arrays compared to the films, which can be attributed to the high surface-to-volume ratio in the nanorod arrays. Our FMR measurements showed low effective damping parameters of (4-8) × 10−3 in both nanorods and film structures. These observations are promising for future nonlinear optoelectronics and spintronics applications.
Absence of detectable spin and orbital pumping from Ni to Nb by out-of-plane ferromagnetic resonance
Bakare, Omolara A.; Street, Galen T.; Abdizadeh, Sachli; Maizel, Rachel E.; Klewe, Christoph; Emori, Satoru (AIP Publishing, 2026-02-02)
Excited ferromagnets can pump spin angular momentum, along with possibly orbital angular momentum. Among elemental ferromagnets, Ni has been proposed to exhibit substantial orbital pumping relative to spin pumping. Here, we search for a signature of orbital pumping by Ni, specifically by comparing out-of-plane ferromagnetic resonance in heterostructures without Ni (FeV/Nb) and with Ni (FeV-Ni/Nb). The FeV/Nb series shows a clear increase in Gilbert damping with the Nb sink thickness, attributed to spin pumping from FeV to Nb. Surprisingly, the FeV-Ni/Nb series exhibits no such damping increase, revealing no significant spin or orbital pumping from Ni to Nb. Our results offer a fresh perspective on angular-momentum transfer in Ni/Nb heterostructures.
New Constraints on the Evolution of the MH i-M☆ Scaling Relation Combining CHILES and MIGHTEE-H i Data
Bianchetti, Alessandro; Sinigaglia, Francesco; Rodighiero, Giulia; Elson, Ed; Vaccari, Mattia; Pisano, D. J.; Luber, Nicholas; Prandoni, Isabella; Hess, Kelley; Baes, Maarten; Adams, Elizabeth A. K.; Maccagni, Filippo M.; Renzini, Alvio; Bisigello, Laura; Yun, Min; Momjian, Emmanuel; Gim, Hansung B.; Pan, Hengxing; Oosterloo, Thomas A.; Dodson, Richard; Lucero, Danielle; Frank, Bradley S.; Ilbert, Olivier; Davies, Luke J. M.; Khostovan, Ali A.; Salvato, Mara (IOP Publishing, 2025-04-01)
The improved sensitivity of interferometric facilities to the 21 cm line of atomic hydrogen (H i) enables studies of its properties in galaxies beyond the local Universe. In this work, we perform a 21 cm line spectral stacking analysis combining the MeerKAT International GigaHertz Tiered Extragalactic Exploration and COSMOS H i Large Extra-galactic Survey surveys in the COSMOS field to derive a robust H i-stellar mass relation at z ≈ 0.36. In particular, by stacking thousands of star-forming galaxies subdivided into stellar mass bins, we optimize the signal-to-noise ratio of targets and derive mean H i masses in the different stellar mass intervals for the investigated galaxy population. We combine spectra from the two surveys, estimate H i masses, and derive the scaling relation log 10 M H I = ( 0.32 ± 0.04 ) log 10 M ⋆ + ( 6.65 ± 0.36 ) . Our findings indicate that galaxies at z ≈ 0.36 are H i richer than those at z ≈ 0 but H i poorer than those at z ≈ 1, with a slope consistent across redshift, suggesting that stellar mass does not significantly affect H i exchange mechanisms. We also observe a slower growth rate H i relative to the molecular gas, supporting the idea that the accretion of cold gas is slower than the rate of consumption of molecular gas to form stars. This study contributes to understanding the role of atomic gas in galaxy evolution and sets the stage for future development of the field in the upcoming Square Kilometre Array era.
Gas-rich dwarf galaxy multiples in the Apertif HI survey
Siljeg, B.; Adams, E. A. K.; Fraternali, F.; Hess, K. M.; Marasco, A.; Denes, H.; Garrido, J.; Lucero, Danielle M.; Morganti, R.; Sanchez-Exposito, S.; van der Hulst, J. M. (EDP Sciences, 2025-11-26)
Context. Dwarf-dwarf galaxy encounters are a key aspect of galaxy evolution as they can ignite or temporarily suppress star formation in dwarfs and can lead to dwarf mergers. However, the frequency and impact of dwarf encounters remain poorly constrained due to limitations in spectroscopic studies, such as surface-brightness incompleteness in optical studies and poor spatial resolution in single-dish neutral hydrogen (H I) surveys.
Aims. We aim to quantify the frequency of isolated gas-rich dwarf galaxy multiples using the untargeted, interferometric Apertif H I survey and study the impact of the interaction on star formation rates of galaxies as a function of the on-sky separation.
Methods. Our parent dwarf sample consists of 2481 gas-rich galaxies with stellar masses in the range ∼106 < M ⋆/M ⊙ ≲ 5 × 109, for which we identified close companions based on projected separation (r p) and systemic velocity difference (|ΔV sys|). We explored both constant thresholds for r p and |ΔV sys| corresponding to 150 kpc and 150 km s−1 on all galaxies in our sample as well as mass-dependent thresholds based on a stellar-to-halo mass relation.
Results. We find the average number of companions per dwarf in our sample to be 13% (20%) when considering mass-dependent (constant) thresholds. We find that the frequency (∼11.6%) of dwarf companions in the stellar mass regime of 2 × 108 < M ⋆/M ⊙ < 5 × 109 is three times higher than previously determined from optical spectroscopic studies, highlighting the power of H I for finding dwarf multiples. Furthermore, we find evidence for an increase in star formation rates (SFRs) of close dwarf galaxy pairs of galaxies with similar stellar masses.
Bridging the gap: Biomechanics of vertical gap-crossing in snakes and cicadas
Pulliam, Joshua Nicholas (Virginia Tech, 2026-02-13)
The ability to locomote through arboreal environments is essential for the animals which make those environments their home. An animal's ability to move among branches can depend on both environmental features, such as branch diameter or discontinuities in branch support, as well as the animals' features such as claws, sticky toe pads, or the presence or absence of limbs. Periodical cicadas (Magicada septendecim) are an example of animals which must overcome both discontinuities and changes in branch diameter. After spending 13-17 years of their lives underground, periodical cicadas burrow their way to the surface, climb trees to molt into adults, and then climb to the edges of branches, mate, and oviposit their eggs. Both nymphs and adults must overcome the same surfaces, yet how the environmental factors of these surfaces interact with the age of the subject to influence climbing performance remains unknown. Additionally, the influence of arboreal surface structure on animal locomotion is not limited to insects, or even limbed animals. Limbless animals, such as arboreal snakes, must contend with these same issues. While perch diameter's effects on horizontal locomotor speed and balance have been well explored, its influence on limbless animal's abilities to cross vertical gaps between branches remains relatively understudied. Despite perch diameter's known influence on an animal's ability to prevent toppling, no study has recorded how this influence translates to its influence on vertical gap crossing ability for limbless animals. This dissertation seeks to answer how arboreal surface structures shape locomotor performance across diverse taxa. Chapter 2 presents a study asking how increasing perch diameter and varying surface friction influences adult periodical cicadas ability to navigate cylindrical surfaces, showing that, at smaller diameters, cicadas are able to cross distances which proved difficult to impossible at larger diameters. Chapter 3 expands on this, exploring gap size's relationships with successful climbs but also compares the performance of adult cicadas to those of nymphs. Additionally, a series of trials are introduced within this chapter to explore surface roughness's influence on climbing capability for both age groups, revealing relationships between surface roughness and success for both age groups, as well as age groups and how well they succeed, defined by how quickly they completed the cross. Finally, Chapter 4 explores diameter's influence on vertical gap crossing in arboreal snakes, exploring factors such as the heights they reach, the speed at which they reach these heights, how well they maintain balance in doing so, and the torque the portion of the bodies within the gap experience. My results have found that perch diameter does influence several performance variables in arboreal locomotion for cicadas and snakes. These variables include, but are not limited to, maximum size of gaps possible to cross for the former, and heights reached for the latter. Additionally, I found that age groups influence the performance of periodical cicadas on climbing structures, while the surface conditions of these structures influence their ability to successfully climb.