We analytically and experimentally show how voltage modulation of a microfabricated piezo-optomechanical magnetic field sensor improves performance at Super Low Frequencies, an especially important frequency range not currently served by microfabricated optomechanical magnetometers.

This work investigates a compact, resonant magnetoelectric transmitter for near-field communication in RF-denied environments. The transmitter leverages a Tonpilz-type resonator, employing a laminated Galfenol bar mechanically coupled to a single crystal 0.24Pb(In1/2Nb1/2)O-3-0.46Pb(Mg1/3Nb2/3)O-3-0.30PbTiO(3) (PIN-PMN-PT) piezoelectric element. Driven at its longitudinal resonance mode around 4 kHz, the piezoelectric element induces stress in the Galfenol bar, generating a magnetic dipole field via the magnetostrictive effect. Rigorous characterization, including impedance, quality factor, internal dynamic flux, and transmitted magnetic signal measurements, was performed. Notably, the device's resonant frequency can be tuned within the 3-6 kHz range by adjusting the DC bias voltage applied to the piezoelectric element or by modifying the compressive prestress. Operating at resonance yields a tenfold amplification of the magnetic dipole signal, which extrapolates to a radiative field strength of approximately 1 fT at 100 m requiring only 0.637 Wrms of power. Strong agreement between experimental data and theoretical models highlights the critical role of device geometry in optimizing the transmitter design for enhanced field generation. (c) 2025 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International (CC BY-NC-ND) license (

This work presents the development of a magnetic rheostat, a dynamically tunable magnetic circuit element analogous to a variable resistor, leveraging the stress-dependent permeability of magnetostrictive materials. Dynamic and precise control of a magnetic field is increasingly critical for diverse applications, yet traditional methods such as electromagnets suffer from power consumption and size limitations. This magnetic rheostat offers a nonvolatile, energy-efficient alternative. The device utilizes Galfenol (Fe1-xGax, x = 0.17 - 0.19), whose permeability decreases under compressive stress to demonstrate stress-induced modulation of the magnetic flux density within an air gap. A fabricated prototype, comprising a Galfenol flux conduction element mechanically coupled to a lead-zirconate-titanate piezoelectric actuator for stress application, exhibits a magnetoelectric coupling coefficient of -0.659 mT/V and tuning of the flux density from 176.6 to 85.5 mT within a gap element. This multiferroic approach, based on stress-mediated permeability changes, demonstrates the feasibility of dynamic, non-current based flux control and opens new avenues for designing tunable magnetic circuits for diverse applications requiring precise magnetic field manipulation. The inherent nonlinearity of ferromagnetic materials, while presenting design challenges related to saturation effects, also offers opportunities for performance optimization through tailored geometry and stress application methods.

Magnetic field sensors that can operate at temperatures above 300 degrees C are necessary for sensing in harsh environments. A strain-modulated sensor composed of AlN and FeCo paired with an AlNiCo magnetic bias circuit and FeCoV flux concentrators capable of operation from 25 to 500 degrees C is presented. The total package size, including the bias circuit and flux concentrators, is 0.4 cm(3), and at 500 degrees C, the noise spectral density of this sensor is 26 nT/root Hz for a 100 Hz signal. At 500 degrees C, the sensor has a Q factor of 1366 and a theoretical bandwidth of 2.5 kHz. The noise spectral density and sensitivity are reported for various temperatures as the temperature is heated from 25 to 500 degrees C and subsequently cooled from 500 to 25 degrees C.

Magnetic fields produced by the body can provide information for medical diagnoses, patient monitoring, and robotic control. Measuring biomagnetic signals locally allows for an external sensing mechanism that is non-invasive and non-contact. Despite these advantages, current sensing systems are either prohibitively large, consume excessive power, or both when applied to on-body applications. This study explores how multiferroic systems can provide an alternative to current biomagnetic sensing platforms. While maintaining a very small die size (2.25mm2) and low power consumption (13mW), multiferroic resonant MEMS magnetometers can provide high sensitivity and low noise at room temperature. Two resonant plate designs operating in the MHz regime are explored, implementing a strain modulation technique to upconvert low frequency magnetic field signals to the resonance band of the plates, utilizing the high device Q factors. When operated below the Duffing limit, sensitivities of 58.4mA/T and 37.7mA/T with resolutions of 5.03nT/ $\surd $ Hz and 2.72nT/ $\surd $ Hz, respectively, were observed for the two devices. Without electric modulation, the large sensor design shows a sensitivity of 1.56A/T and a resolution of 2pT/ $\surd $ Hz when sensing an AC magnetic field at the device resonance. [2022-0158]

Low noise sensors with low power consumption are needed for sensing the biomagnetic potentials produced by the human body. Compared to their electrical counterparts, biomagnetic sensors are noninvasive and noncontact. A strain-modulated FeCo-Hf/AlScN-based sensor with a bandwidth of 3.4 kHz and a magnetic noise spectral density at 1 kHz of 59.5 pT/ $\surd $ Hz before demodulation and 98.5 pT/ $\surd $ Hz after demodulation in an unshielded environment is presented. The footprint of the sensor including flux concentrators is 0.125 cm 2 , and the total power consumption of the printed circuit board (PCB)-based readout electronics is 440 mW. A theoretical analysis for the scaling of the sensitivity and the noise spectral density of modulated multiferroic sensor systems is presented.

Angular dependence of magnetic field response of fully suspended resonant microelectromechanical double-clamped magnetoelectric beams was investigated as the basis for a vector magnetometer utilizing the magnetically induced change in fundamental resonance frequency. Strain-coupled magnetostrictive iron cobalt (FeCo) and piezoelectric aluminum nitride layers together constitute a magnetoelectric heterostructure with a high magnetic field sensitivity of 70Hz/mT along the beam axis and a transfer function of 47V/T at 10Hz. The fundamental frequency shift to an external magnetic field is found to be strongly anisotropic with a relative variation of more than 3% between perpendicular and parallel field orientations with respect to the long axis of the beam at a field of 100mT. This design can form the basis for an on-chip high sensitivity vector magnetometer operating with ultra-low power when multiplexed with two or more resonators.

Materials with high magnetoelectric coupling are attractive for use in engineered multiferroic heterostructures with applications such as ultra-low power magnetic sensors, parametric inductors, and non-volatile random-access memory devices. Iron–cobalt alloys exhibit both high magnetostriction and high saturation magnetization that are required for achieving significantly higher magnetoelectric coupling. We report on sputter-deposited (Fe0.5Co0.5)1−xHfx (x = 0 – 0.14) alloy thin films and the beneficial influence of Hafnium alloying on the magnetic and magnetostrictive properties. We found that co-sputtering Hf results in the realization of the peening mechanism that drives film stress from highly tensile to slightly compressive. Scanning electron microscopy and x-ray diffraction along with vibrating sample magnetometry show reduction in coercivity with Hf alloying that is correlated with reduced grain size and low film stress. We demonstrate a crossover from tensile to compressive stress at x ∼ 0.09 while maintaining a high magnetostriction of 50 ppm and a low coercive field of 1.1 Oe. These characteristics appear to be related to the amorphous nature of the film at higher Hf alloying.

Magnetoelectric (ME)-based magnetometers have garnered much attention as they boast ultra-low-power systems with a small form factor and limit of detection in the tens of picotesla. The highly sensitive and low-power electric readout from the ME sensor makes them attractive for near DC and low-frequency AC magnetic fields as platforms for continuous magnetic signature monitoring. Among multiple configurations of the current ME magnetic sensors, most rely on exploiting the mechanically resonant characteristics of a released ME microelectromechanical system (MEMS) in a heterostructure device. Through optimizing the resonant device configuration, we design and fabricate a fixed–fixed resonant beam structure with high isolation compared to previous designs operating at ~800 nW of power comprised of piezoelectric aluminum nitride (AlN) and magnetostrictive (Co1-xFex)-based thin films that are less susceptible to vibration while providing similar characteristics to ME-MEMS cantilever devices. In this new design of double-clamped magnetoelectric MEMS resonators, we have also utilized thin films of a new iron–cobalt–hafnium alloy (Fe0.5Co0.5)0.92Hf0.08 that provides a low-stress, high magnetostrictive material with an amorphous crystalline structure and ultra-low magnetocrystalline anisotropy. Together, the improvements of this sensor design yield a magnetic field sensitivity of 125 Hz/mT when released in a compressive state. The overall detection limit of these sensors using an electric field drive and readout are presented, and noise sources are discussed. Based on these results, design parameters for future ME MEMS field sensors are discussed.

Electrical switching of ferroelectric domains and subsequent domain wall motion promotes strong piezoelectric activity, however, light scatters at refractive index discontinuities such as those found at domain wall boundaries. Thus, simultaneously achieving large piezoelectric effect and high optical transmissivity is generally deemed infeasible. Here, it is demonstrated that the ferroelectric domains in perovskite Pb(In1/2 Nb1/2 )O3 -Pb(Mg1/3 Nb2/3 )O3 -PbTiO3 domain-engineered crystals can be manipulated by electrical field and mechanical stress to reversibly and repeatably, with small hysteresis, transform the opaque polydomain structure into a highly transparent monodomain state. This control of optical properties can be achieved at very low electric fields (less than 1.5 kV cm-1 ) and is accompanied by a large (>10 000 pm V-1 ) piezoelectric coefficient that is superior to linear state-of-the-art materials by a factor of three or more. The coexistence of tunable optical transmissivity and high piezoelectricity paves the way for a new class of photonic devices.

SummaryMultiferroic resonant MEMS magnetometers show great promise to provide a highly sensitive, low noise option for detecting low frequency magnetic fields at room temperature and in a small form factor. Strain modulation techniques enable sensitivity enhancement by the high device Q factors. However, as the strain modulation increases, a resonator Duffing nonlinearity is observed before the magnetostrictive material can be sufficiently strained to provide high modulation efficiency. Here, we report a multiferroic resonant MEMS magnetometer with a sensitivity of 32mArms/T and noise value of ~2.2nT/√Hz.

Due to the novel optical and optoelectronic properties, two dimensional (2D) materials have received increasing interests for optoelectronics applications. Discovering new properties and functionalities of 2D materials are challenging yet promising. Here broadband polarization sensitive photodetectors based on few layer ReS2 are demonstrated. The transistor based on few layer ReS2 shows an n-type behavior with the mobility of about 40 cm 2 V -1 s -1 and on/off ratio of 10 5 . The polarization dependence of photoresponse is ascribed to the unique anisotropic in-plane crystal structure, consistent with the optical absorption

The unconventional electronic ground state of Sr_3IrRuO_7 is explored via resonant x-ray scattering techniques and angle-resolved photoemission measurements. As the Ru content approaches x=0.5 in Sr_3(Ir_1-xRu_x)_2O_7, intermediate to the J_eff=1/2 Mott state in Sr_3Ir_2O_7 and the quantum critical metal in Sr_3Ru_2O_7, a thermodynamically distinct metallic state emerges. The electronic structure of this intermediate phase lacks coherent quasiparticles, and charge transport exhibits a linear temperature dependence over a wide range of temperatures. Spin dynamics associated with the long-range antiferromagnetism of this phase show nearly local, overdamped magnetic excitations and an anomalously large energy scale of 200 meV—an energy far in excess of exchange energies present within either the Sr_3Ir_2O_7 or Sr_3Ru_2O_7 solid-solution endpoints. Overdamped quasiparticle dynamics driven by strong spin-charge coupling are proposed to explain the incoherent spectral features of the strange metal state in Sr_3IrRuO_7.

Due to the novel optical and optoelectronic properties, 2D materials have received increasing interests for optoelectronics applications. Discovering new properties and functionalities of 2D materials is challenging yet promising. Here broadband polarization sensitive photodetectors based on few layer ReS2 are demonstrated. The transistor based on few layer ReS2 shows an n‐type behavior with the mobility of about 40 cm2 V−1 s−1 and on/off ratio of 105. The polarization dependence of photoresponse is ascribed to the unique anisotropic in‐plane crystal structure, consistent with the optical absorption anisotropy. The linear dichroic photodetection with a high photoresponsivity reported here demonstrates a route to exploit the intrinsic anisotropy of 2D materials and the possibility to open up new ways for the applications of 2D materials for light polarization detection.

Unraveling the nature of pseudogap phase in high-temperature superconductors holds the key to understanding their superconducting mechanisms and potentially broadening their applications via enhancement of their superconducting transition temperatures. Angle-resolved photoemission spectroscopy (ARPES) experiments using circularly polarized light have been proposed to detect possible symmetry breaking state in the pseudogap phase of cuprates. The presence (absence) of an electronic order which breaks mirror symmetry of the crystal would in principle induce a finite (zero) circular dichroism in photoemission. Different orders breaking reflection symmetries about different mirror planes can also be distinguished by the momentum dependence of the measured circular dichroism. Here, we report ARPES experiment on an underdoped Bi2Sr2CaCu2O8+δ (Bi2212) superconductor in the Γ (0,0)-Y (π,π) nodal mirror plane using circularly polarized light. No circular dichroism is observed on the level of ∼2% at low temperature, which places a clear constraint on the forms of possible symmetry breaking orders in this sample. Meanwhile, we find that the geometric dichroism remains substantial very close to its perfect extinction such that a very small sample angular offset is sufficient to induce a sizeable dichroic signal. It highlights the importance to establish a perfect extinction of geometric dichroism as a prerequisite for the identification of any intrinsic circular dichroism in this material.

Advanced Functional MaterialsVolume 26, Issue 8 p. 1146-1146 Inside Front CoverFree Access Photoresponse: Highly Sensitive Detection of Polarized Light Using Anisotropic 2D ReS2 (Adv. Funct. Mater. 8/2016) Fucai Liu, Fucai Liu School of Materials Science and Engineering, Nanyang Technological University, Singapore, 639798 SingaporeSearch for more papers by this authorShoujun Zheng, Shoujun Zheng Centre for Disruptive Photonic Technologies, School of Physics and Mathematics Sciences, Nanyang Technological University, Singapore, 637371 SingaporeSearch for more papers by this authorXuexia He, Corresponding Author Xuexia He School of Materials Science and Engineering, Nanyang Technological University, Singapore, 639798 SingaporeSearch for more papers by this authorApoorva Chaturvedi, Apoorva Chaturvedi School of Materials Science and Engineering, Nanyang Technological University, Singapore, 639798 SingaporeSearch for more papers by this authorJunfeng He, Junfeng He Department of Physics, Boston College, Chestnut Hill, MA, 02467 USASearch for more papers by this authorWai Leong Chow, Wai Leong Chow NOVITAS, Centre for Micro-/Nano-electronics School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore, 639798 Singapore CINTRA CNRS/NTU/THALES, UMI 3288, Research Techno Plaza, 50 Nanyang Drive, Border X Block Level 6, Singapore, 637553 SingaporeSearch for more papers by this authorThomas R. Mion, Thomas R. Mion Department of Physics, Boston College, Chestnut Hill, MA, 02467 USASearch for more papers by this authorXingli Wang, Xingli Wang NOVITAS, Centre for Micro-/Nano-electronics School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore, 639798 SingaporeSearch for more papers by this authorJiadong Zhou, Jiadong Zhou School of Materials Science and Engineering, Nanyang Technological University, Singapore, 639798 SingaporeSearch for more papers by this authorQundong Fu, Qundong Fu School of Materials Science and Engineering, Nanyang Technological University, Singapore, 639798 SingaporeSearch for more papers by this authorHong Jin Fan, Hong Jin Fan Centre for Disruptive Photonic Technologies, School of Physics and Mathematics Sciences, Nanyang Technological University, Singapore, 637371 SingaporeSearch for more papers by this authorBeng Kang Tay, Beng Kang Tay NOVITAS, Centre for Micro-/Nano-electronics School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore, 639798 Singapore CINTRA CNRS/NTU/THALES, UMI 3288, Research Techno Plaza, 50 Nanyang Drive, Border X Block Level 6, Singapore, 637553 SingaporeSearch for more papers by this authorLi Song, Li Song National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, Anhui, 230026 P. R. ChinaSearch for more papers by this authorRui-Hua He, Rui-Hua He Department of Physics, Boston College, Chestnut Hill, MA, 02467 USASearch for more papers by this authorChristian Kloc, Christian Kloc School of Materials Science and Engineering, Nanyang Technological University, Singapore, 639798 SingaporeSearch for more papers by this authorPulickel M. Ajayan, Pulickel M. Ajayan Department of Materials Science and Nanoengineering, Rice University, Houston, TX, 77005 USASearch for more papers by this authorZheng Liu, Corresponding Author Zheng Liu NOVITAS, Centre for Micro-/Nano-electronics School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore, 639798 Singapore CINTRA CNRS/NTU/THALES, UMI 3288, Research Techno Plaza, 50 Nanyang Drive, Border X Block Level 6, Singapore, 637553 Singapore Center for Programmable Materials School of Materials Science and Engineering, Nanyang Technological University, Singapore, 639798 SingaporeSearch for more papers by this author Fucai Liu, Fucai Liu School of Materials Science and Engineering, Nanyang Technological University, Singapore, 639798 SingaporeSearch for more papers by this authorShoujun Zheng, Shoujun Zheng Centre for Disruptive Photonic Technologies, School of Physics and Mathematics Sciences, Nanyang Technological University, Singapore, 637371 SingaporeSearch for more papers by this authorXuexia He, Corresponding Author Xuexia He School of Materials Science and Engineering, Nanyang Technological University, Singapore, 639798 SingaporeSearch for more papers by this authorApoorva Chaturvedi, Apoorva Chaturvedi School of Materials Science and Engineering, Nanyang Technological University, Singapore, 639798 SingaporeSearch for more papers by this authorJunfeng He, Junfeng He Department of Physics, Boston College, Chestnut Hill, MA, 02467 USASearch for more papers by this authorWai Leong Chow, Wai Leong Chow NOVITAS, Centre for Micro-/Nano-electronics School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore, 639798 Singapore CINTRA CNRS/NTU/THALES, UMI 3288, Research Techno Plaza, 50 Nanyang Drive, Border X Block Level 6, Singapore, 637553 SingaporeSearch for more papers by this authorThomas R. Mion, Thomas R. Mion Department of Physics, Boston College, Chestnut Hill, MA, 02467 USASearch for more papers by this authorXingli Wang, Xingli Wang NOVITAS, Centre for Micro-/Nano-electronics School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore, 639798 SingaporeSearch for more papers by this authorJiadong Zhou, Jiadong Zhou School of Materials Science and Engineering, Nanyang Technological University, Singapore, 639798 SingaporeSearch for more papers by this authorQundong Fu, Qundong Fu School of Materials Science and Engineering, Nanyang Technological University, Singapore, 639798 SingaporeSearch for more papers by this authorHong Jin Fan, Hong Jin Fan Centre for Disruptive Photonic Technologies, School of Physics and Mathematics Sciences, Nanyang Technological University, Singapore, 637371 SingaporeSearch for more papers by this authorBeng Kang Tay, Beng Kang Tay NOVITAS, Centre for Micro-/Nano-electronics School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore, 639798 Singapore CINTRA CNRS/NTU/THALES, UMI 3288, Research Techno Plaza, 50 Nanyang Drive, Border X Block Level 6, Singapore, 637553 SingaporeSearch for more papers by this authorLi Song, Li Song National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, Anhui, 230026 P. R. ChinaSearch for more papers by this authorRui-Hua He, Rui-Hua He Department of Physics, Boston College, Chestnut Hill, MA, 02467 USASearch for more papers by this authorChristian Kloc, Christian Kloc School of Materials Science and Engineering, Nanyang Technological University, Singapore, 639798 SingaporeSearch for more papers by this authorPulickel M. Ajayan, Pulickel M. Ajayan Department of Materials Science and Nanoengineering, Rice University, Houston, TX, 77005 USASearch for more papers by this authorZheng Liu, Corresponding Author Zheng Liu NOVITAS, Centre for Micro-/Nano-electronics School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore, 639798 Singapore CINTRA CNRS/NTU/THALES, UMI 3288, Research Techno Plaza, 50 Nanyang Drive, Border X Block Level 6, Singapore, 637553 Singapore Center for Programmable Materials School of Materials Science and Engineering, Nanyang Technological University, Singapore, 639798 SingaporeSearch for more papers by this author First published: 22 February 2016 https://doi.org/10.1002/adfm.201670048Citations: 13AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Abstract Light polarization is an important concept in optics for generation, detection and manipulation of light. ReS2, a highly anisotropic two-dimensional material, has excellent capabilities for high detection sensitivity of polarized light, as shown by X. He, Z. Liu, and co-workers on page 1169. Atomically thin ReS2 may pave a promising way to applications in integrated photonic circuits, optical switches and interconnects for detecting the various orientations of linearly polarized light in a highly integrated photonic platform. Citing Literature Volume26, Issue8February 23, 2016Pages 1146-1146 RelatedInformation

Recent developments in high-temperature superconductivity highlight a generic tendency of the cuprates to develop competing electronic (charge) supermodulations. While coupled with the lattice and showing different characteristics in different materials, these supermodulations themselves are generally conceived to be quasi-two-dimensional, residing mainly in individual CuO2 planes, and poorly correlated along the c axis. Here we observed with resonant elastic X-ray scattering a distinct type of electronic supermodulation in YBa2Cu3O(7-x) (YBCO) thin films grown epitaxially on La0.7Ca0.3MnO3 (LCMO). This supermodulation has a periodicity nearly commensurate with four lattice constants in-plane, eight out of plane, with long correlation lengths in three dimensions. It sets in far above the superconducting transition temperature and competes with superconductivity below this temperature for electronic states predominantly in the CuO2 plane. Our finding sheds light on the nature of charge ordering in cuprates as well as a reported long-range proximity effect between superconductivity and ferromagnetism in YBCO/LCMO heterostructures.

Negative compressibility is a sign of thermodynamic instability of open or non-equilibrium systems. In quantum materials consisting of multiple mutually coupled subsystems, the compressibility of one subsystem can be negative if it is countered by positive compressibility of the others. Manifestations of this effect have so far been limited to low-dimensional dilute electron systems. Here, we present evidence from angle-resolved photoemission spectroscopy (ARPES) for negative electronic compressibility (NEC) in the quasi-three-dimensional (3D) spin-orbit correlated metal (Sr1-xLax)3Ir2O7. Increased electron filling accompanies an anomalous decrease of the chemical potential, as indicated by the overall movement of the deep valence bands. Such anomaly, suggestive of NEC, is shown to be primarily driven by the lowering in energy of the conduction band as the correlated bandgap reduces. Our finding points to a distinct pathway towards an uncharted territory of NEC featuring bulk correlated metals with unique potential for applications in low-power nanoelectronics and novel metamaterials.