arXiv subjects

Michael Newburger

Publications and source records attributed to Michael Newburger.

7 recordsLinked to original sources

arXiv2026

Magneto Transport and Spin Reorientation in Pt Co78Ho22 Heterostructures Near the Sublattice Compensation Temperature

Metallic amorphous ferrimagnets of 3d transition metals (TM) and rare earths (RE) with 4f electrons exhibit rich magneto transport behavior due to the interplay between the 3d and 4f magnetic sublattices and their interaction with mobile charges. Tuning the TM and RE concentrations in the alloy can effectively modulate the compensation temperature, where the moments of the two sublattices point in opposite direction leading to a net zero magnetization. Despite extensive magnetotransport studies in Gd and Tb based 3d 4f systems, Ho based alloys remain comparatively underexplored, even though Ho possesses the largest orbital angular momentum (OAM) among the lanthanides. This unquenched OAM can strongly impact magnetic anisotropy and magnetotransport in ferrimagnetic heterostructures. Here, we have investigated the anomalous Hall resistivity , dc magnetization, and spin Hall magnetoresistance (SHMR) of Co78Ho22.Al film and a Pt.Co78Ho22.Al heterostructure deposited using multitarget magnetron sputtering. The Hall resistivity of both systems shows a distinct sign reversal and prominent wing-shaped hysteresis loops in the vicinity of the compensation temperature (Tcomp), which is accompanied by the minimum saturation magnetization near Tcomp. Furthermore, the SHMR in Pt.Co78Ho22.Al film is enhanced due to the Pt layer. These HM interface-induced prominent features of magneto-transport are addressed in the light of the existing theories of spin flop transitions, spin orbit torque, and microscopic phase separation, which may lead to the formation of 3d and 4f magnetic clusters in the film.

cond-mat.mtrl-sci↗

arXiv2025

Roadmap: 2D Materials for Quantum Technologies

Two-dimensional (2D) materials have emerged as a versatile and powerful platform for quantum technologies, offering atomic-scale control, strong quantum confinement, and seamless integration into heterogeneous device architectures. Their reduced dimensionality enables unique quantum phenomena, including optically addressable spin defects, tunable single-photon emitters, low-dimensional magnetism, gate-controlled superconductivity, and correlated states in Moir\'e superlattices. This Roadmap provides a comprehensive overview of recent progress and future directions in exploiting 2D materials for quantum sensing, computation, communication, and simulation. We survey advances spanning spin defects and quantum sensing, quantum emitters and nonlinear photonics, computational theory and data-driven discovery of quantum defects, spintronic and magnonic devices, cavity-engineered quantum materials, superconducting and hybrid quantum circuits, quantum dots, Moir\'e quantum simulators, and quantum communication platforms. Across these themes, we identify common challenges in defect control, coherence preservation, interfacial engineering, and scalable integration, alongside emerging opportunities driven by machine$-$learning$-$assisted design and integrated experiment$-$theory feedback loops. By connecting microscopic quantum states to mesoscopic excitations and macroscopic device architectures, this Roadmap outlines a materials-centric framework for integrating coherent quantum functionalities and positions 2D materials as foundational building blocks for next-generation quantum technologies.

quant-ph↗

arXiv2025

Ferroelectric Epsilon-WO3 Nanoparticles and Its Bipolaron Driven Opto-electronic Properties at Room Temperature

A unique polymorph of binary tungsten trioxide, the epsilon phase of WO3, has non-centrosymmetric ferroelectric structure, typically stable below -43 degree C in bulk. We have stabilized the epsilon-WO3 at room temperature (RT) and nanostructured powders via flame spray pyrolysis synthesis. These nanopowders are drop cast into uniform thin films to enable RT measurement of ferroelectric and optoelectronic properties. We report ferroelectric hysteresis, nanoscale domains, and dipole switching measured via Piezo-response force microscopy (PFM). The epsilon-WO3 films also display optical second harmonic generation (SHG) and anticlockwise ferroelectric butterfly capacitance versus voltage hysteresis, further demonstrating the ferroelectric nature of epsilon-WO3. Remarkably, epsilon-WO3 shows ferroelectric polarization responses to optical stimuli and form bipolaron at RT, a spin-zero quasiparticle previously found only in cryogenic temperatures. The bipolaron formation and its interaction with electro-optical stimuli results in a single layer solid-state blue coloration, a ferrochromic effect. A mechanism of the ferrochromic effect is discussed. In summary, epsilon-WO3 appears to be a ferroelectric with the simplest structure, forming bosonic spin-zero bipolaron at RT, and it's dipoles respond to opto-electrical signals; therefore, this material holds significant promise for transforming the field of optoelectronics.

cond-mat.mtrl-sci↗

arXiv2025

Exploring Weak Turbulence of Phonon and Magnon Beams in Magneto-Acoustic Ultrathin Films

This study presents a simple theoretical model describing narrow envelope surface acoustic waves (phonons) and spin waves (magnons) in an ultrathin ferromagnetic film. Based on the general principles of weak wave turbulence, the model considers interactions between beams of an ideal phonon gas and a weakly non-ideal magnon gas, which represent magnetoacoustic oscillations in the system. Equations for the wave envelopes of phonons and magnons, along with their harmonics, are derived, incorporating nonlinear effects from three- and four-particle interactions. In the general non-resonant case, linear stationary envelope simulations are sufficient. These clarify the experimentally observed angular dependence of the transmitted acoustic signal with respect to the orientation of the magnetic field. The study highlights increased energy losses associated with enhanced magnetoacoustic coupling. Given the broad interdisciplinary interest in weak turbulence phenomena within condensed matter physics and nonlinear wave dynamics, our model offers significant predictive capabilities and greatly simplifies calculations of quasiparticle beam interactions.

cond-mat.other↗

arXiv2025

Electrical Side-Gate Control of Anisotropic Magnetoresistance and Magnetic Anisotropy in a Composite Multiferroic

Composite multiferroics consisting of a ferroelectric material interfaced with a ferromagnetic material can function above room temperature and exhibit improved magnetoelectric (ME) coupling compared to single-phase multiferroic materials, making them desirable for applications in energy efficient electronic devices. In this study, we demonstrate electrical side-gate control of magnetoresistance and magnetic anisotropy in single-crystalline ferromagnetic Fe$_{0.75}$Co$_{0.25}$ thin films grown on ferroelectric PMN-PT (001) substrates by molecular beam epitaxy. Fe$_{0.75}$Co$_{0.25}$ is selected due to its large magnetoelastic coupling and low magnetic damping. We find that the magnetoresistance curves of patterned Fe$_{0.75}$Co$_{0.25}$ films are controlled by voltages applied to electrostatic side gates. Angle-dependent magnetoresistance scans reveal that the origin of this effect is strain-mediated variation of the magnetic anisotropy due to piezoelectric effects in the PMN-PT. This electrical control of magnetic properties could serve as a building block for future magnetoelectronic and magnonic devices.

cond-mat.mtrl-sci↗

arXiv2023

Symmetry and nonlinearity of spin wave resonance excited by focused surface acoustic waves

The use of a complex ferromagnetic system to manipulate GHz surface acoustic waves is a rich current topic under investigation, but the high-power nonlinear regime is under-explored. We introduce focused surface acoustic waves, which provide a way to access this regime with modest equipment. Symmetry of the magneto-acoustic interaction can be tuned by interdigitated transducer design which can introduce additional strain components. Here, we compare the impact of focused acoustic waves versus standard unidirectional acoustic waves in significantly enhancing the magnon-phonon coupling behavior. Analytical simulation results based on modified Landau-Lifshitz-Gilbert theory show good agreement with experimental findings. We also report nonlinear input power dependence of the transmission through the device. This experimental observation is supported by the micromagnetic simulation using mumax3 to model the nonlinear dependence. These results pave the way for extending the understanding and design of acoustic wave devices for exploration of acoustically driven spin wave resonance physics.

cond-mat.mtrl-sci↗

arXiv2017

Imaging Spin Dynamics in Monolayer WS2 by Time-Resolved Kerr Rotation Microscopy

Monolayer transition metal dichalcogenides (TMD) have immense potential for future spintronic and valleytronic applications due to their two-dimensional nature and long spin/valley lifetimes. We investigate the origin of these long-lived states in n-type WS2 using time-resolved Kerr rotation microscopy and photoluminescence microscopy with ~1 micron spatial resolution. Comparing the spatial dependence of the Kerr rotation signal and the photoluminescence reveals a correlation with neutral exciton emission, which is likely due to the transfer of angular momentum to resident conduction electrons with long spin/valley lifetimes. In addition, we observe an unexpected anticorrelation between the Kerr rotation and trion emission, which provides evidence for the presence of long-lived spin/valley-polarized dark trions. We also find that the spin/valley polarization in WS2 is robust to magnetic fields up to 700 mT, indicative of spins and valleys that are stabilized with strong spin-orbit fields.

cond-mat.mes-hall↗