Bulletin of the American Physical Society
APS March Meeting 2019
Volume 64, Number 2
Monday–Friday, March 4–8, 2019; Boston, Massachusetts
Session Y39: Magnetic Sensors, Devices, and ApplicationsFocus
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Sponsoring Units: GMAG DMP Chair: Jamileh Mohammadi , New York University Room: BCEC 207 |
Friday, March 8, 2019 11:15AM - 11:27AM |
Y39.00001: PicoTesla Magnetic Sensors based on Magnetic Tunneling Junctions with Double-staged Flux Concentrators Guanyang He, Yiou Zhang, Lijuan Qian, Gang Xiao, Qiang Zhang, J. Carlos Santamarina, Tadeusz W. Patzek, Xixiang Zhang Highly sensitive magnetic tunneling junction (MTJ) sensors have shown great potential as the best miniaturized, low-cost, solid-state magnetic sensors, strongly needed in different applications. We have fabricated high performance MTJ sensors and pushed the magnetic sensing limit to a high level, mainly by incorporating double-staged magnetic flux concentrators (MFC), one on the MTJ chip level and the other on a macroscopic level, to amplify the external field. After multiple optimizations on MFC fabrication conditions, it has increased the sensitivity of the MTJ sensor by a large factor of 517 to 775.4%/Oe in terms of magnetoresistance response. The sensor coercivity is only 0.12 Oe which is desired for sensing application, as we will show that the low-field detectability of magnetic sensor have direct relations with its coercivity. By integrating such MTJ sensors from wafers to integrated circuits, our sensor prototype has achieved detectable field limit of 30pT per root hertz at 10 kHz. We will also present the noise spectrum and the sensitivity spectrum of it and discuss its detectabilities based on these information. |
Friday, March 8, 2019 11:27AM - 11:39AM |
Y39.00002: Circumventing Magnetostatic Reciprocity: a Diode for Magnetic Fields Jordi Prat-Camps, Patrick Maurer, Gerhard Kirchmair, Oriol Romero-Isart Lorentz reciprocity establishes a stringent relation between electromagnetic fields and their sources. For static magnetic fields, a relation between magnetic sources and fields can be drawn in analogy to Green's reciprocity for electrostatics. So far, the magnetostatic reciprocity principle remains unchallenged and the magnetostatic interaction is assumed to be symmetric (reciprocal). Here we show that a linear and isotropic electrically conductive material moving with constant velocity is able to circumvent the magnetostatic reciprocity principle and realize a diode for magnetic fields. This result is demonstrated by measuring an extremely asymmetric magnetic coupling between two coils that are located near a moving conductor. The possibility to generate controlled unidirectional magnetic couplings implies that the mutual inductances between magnetic elements or circuits can be made extremely asymmetric. Other strategies to break magnetic reciprocity based on novel kinds of magnetic metamaterials will be also discussed. |
Friday, March 8, 2019 11:39AM - 11:51AM |
Y39.00003: picoTesla Magnetoelectric Sensors with Low-Curvature Nano-Plate Resonators Alexei Matyushov, Zhenyun Qian, Mohsen Zaeimbashi, Cheng Tu, Huaihao Chen, Menghui Li, matteo rinaldi, Nian Xiang Sun Prior studies have shown the effectiveness of piezoelectric/magnetostrictive MEMS magnetometers featuring a nano plate resonator and using the ΔE effect for highly sensitive detection of DC magnetic fields. By monitoring changes in resonance frequency from applied magnetic fields, a sensitivity of a few Hz/nT has been achieved in unshielded lab environments. With dimensions of ≤ 200 μm across, and < 1 μm thick, these devices offer the advantages of small scale, including portability and low power consumption, as well as high spatial resolution in sensor arrays. However, a thorough understanding of magnetic properties and other performance aspects in these magnetometers has not been developed. In this study we report on the strong effects of resonator plate curvature on sensor performance. It was found that the total resonance frequency shift dropped off exponentially with increasing curvature by as much as two orders of magnitude. By fabricating a ΔE effect magnetometer with low curvature in the nano plate resonator, we achieved maximum magnetic field sensitivity of 4.98 Hz/nT. High frequency stability was also observed: an Allan deviation measurement yielded a minimum of 0.0245 Hz at 100 ms averaging time. This results in a theoretical limit of detection of 1.56 pT/Hz1/2. |
Friday, March 8, 2019 11:51AM - 12:03PM |
Y39.00004: Brain MRI at ultra-low field: new multifunction instrument Koos C J Zevenhoven While conventional MRI uses increasingly high magnetic fields, another approach has emerged, where the signal is detected in an ultra-low field (ULF) on the order of Earth's field. Despite similarities, ULF-MRI differs from high-field MRI in interesting ways. At ULF, the magnetic pulses can be applied silently and with an open-geometry coil system, and the signal can be modeled from theory with high accuracy. The unique possibilities of ULF-MRI also include the combination of MRI and magnetoencephalography (MEG), the measurement of the weak magnetic fields generated by brain activity. ULF-MRI and associated methods such as current-density imaging (CDI) improve the localization of brain activity. |
Friday, March 8, 2019 12:03PM - 12:15PM |
Y39.00005: Finite element study on magnetomechanical properties of magnetorheological elastomer used in advanced mechanical systems. Winnie Kiarie, Neelam Prabhu Gaunkar, David C Jiles, Edward Barron, Michael D. Bartlett Magnetorheological Elastomers (MREs) constitutes a group of materials referred to as ‘smart’ materials. These materials exhibit field-dependent material property which include change in damping and stiffness properties of the material when subjected to an external magnetic field. This paper presents a simulation study of magnetomechanical and thermal properties for a MRE used as a semi-active automotive suspension bushing. Such suspension bushings isolate passengers from the undesirable effects of the surface over which the vehicle is being driven on. It also enhances handling and driving comfort of the driver. The performance of semi-active suspension bushing is highly dependent on the magnetic properties of the MRE. Therefore, electromagnetic simulation using finite element analysis software is used to design and optimize on the MRE suspension bushing’s response to magnetic field. From the finite element analysis, the magnetic flux density developed within the MRE is observed to depend on the permeability, thickness and magnetic shielding of the MRE. |
Friday, March 8, 2019 12:15PM - 12:27PM |
Y39.00006: Highly Sensitive Magnetic Sensor based on Magnetoelectric Effect and Cross-Modulation Technique Cunzheng Dong, Yifan He, Xianfeng Liang, Huaihao Chen, Yuyi Wei, Nian Xiang Sun State of the art bulk magnetoelectric (ME) sensors composed of Metglas/PMN-PT fiber structures have been demonstrated to exhibit a low limit of detection (LOD) of 10 pT at 1 Hz. Because of the low cost and compact size, the ME magnetic field sensor has become competitive to other sensing technologies for applications demand for high sensitivity. The magnetic noise of ME sensors is the key parameter that results from the internal and external noise sources. To reduce the noise level, an active operation mode has been proposed. However, active ME sensors usually show a high magnetic noise over 200 pT/Hz at 1 Hz in the reports. Here, we demonstrate an ultra-sensitive ME sensors based on Metglas/PZT fiber heterostructuers operating at the complete demagnetized state of Metglas. A strong correlation was observed between the limit of detection and the degree of demagnetization of Metglas in the ME sensors, which points to a new way of improving the magnetic field sensitivity of ultra-sensitive ME sensor. Our demonstrated ME sensors based on PZT/Metglas has shown LOD below 2pT and magnetic noise level of 9.1pT/Hz1/2 in the detection of magnetic field at 1Hz, which is one order of magnitude better than other best reported values for PZT/Metglas heterostructures. |
Friday, March 8, 2019 12:27PM - 12:39PM |
Y39.00007: Fabrication and characterization of ultra-soft PDMS based magnetorheological elastomers Andy Clark, Jiajia Li, Lila Hernandez, Vidya Ramaswamy, Elise Corbin, Alexander Bennet, Xuemei Cheng Magnetorheological elastomers (MREs) are composite materials consisting of elastomer matrix with embedded micro- or nano- sized ferromagnetic entities. Ultra-soft PDMS based MREs are promising candidates for dynamic cell culture substrata. In this work, we report the fabrication and magnetic characterization of PDMS based MREs. Sylgard 527 and carbonyl iron powder were mixed together at various ratios and cured at 600C for 24 hours without applied magnetic field and with applied magnetic field of various field strength. Angular dependent magnetic hysteresis loops of MREs were measured using a vibrating sample magnetometer. MREs cured without magnetic field show no angular dependence in the major hysteresis loop, consistent with the isotropic distribution of iron particles in the MREs. Instead, hysteresis loops for MREs cured in magnetic field clearly display anisotropy as expected. The different first order reversal curve (FORC) distribution characteristics of the isotropic and anisotropic MREs agree with the structural difference of these two types of MREs. |
Friday, March 8, 2019 12:39PM - 12:51PM |
Y39.00008: A one-dimensional magnetoelectric sensor array for magnetic sketching Zhaoqiang Chu, Weiliang Shi, Xianfeng Liang, Nian Xiang Sun, Shuxiang Dong Although various magnetic sensors have been developed, it is still a challenge to get the imaging of magnetic objects safely and instantaneously, for example, magnetic imaging for capsule positioning, endoscope navigation, and detection of magnetic weapon that is hidden in/on human body. In this paper, a magnetic detecting and sketching system utilizing a one-dimensional magnetic sensor array with 56 magnetoelectric (ME) sensing units is proposed. The ME sensors used in this system are based on a (1-1) connectivity Metglas/piezo-fiber composite operating in longitudinally magnetized and transversely poled (L-T) mode. Simulation and experiment results show that the proposed magnetic detecting system not only can find the 2-D position of a running magnetic metal object, but also can identify its posture and length-diameter ratio. The proposed magnetic detecting method promises an outlook for medical magnetic positioning and security checking. |
Friday, March 8, 2019 12:51PM - 1:03PM |
Y39.00009: Superparamagnetic Fe3O4 magnetic nanoparticles and their potential for hyperthermia treatment for cancer Bianca Paola Meneses Brassea, Camille Cyr, Israel Martinez, Cristian Botez, Ahmed El-Gendy The heating efficiency of Fe3O4 nanoparticles of different sizes synthesized using supercritical conditions of liquids, under different applied magnetic field intensities and frequencies, was investigated through experimental measurements of specific absorption rate (SAR). The synthesis conditions have been varied in order to obtain different sizes and shapes of Fe3O4 nanoparticles and to examine their effect on the SAR values. The morphology and crystal structure characterization of three samples revealed cubic-like shapes with average sizes of 63, 128, and 91 nm and formation of FCC Fe3O4 phase structure. The magnetic properties were characterized using magnetization dependent of magnetic field and temperature up to 3 T and 400 K respectively. The samples exhibit superparamagnetic-like behavior at room temperature with saturation magnetization Ms of 108, 74, and 77 emu/g and blocking temperatures TB of 320, 235, and 192 K, respectively. SAR values at 400 Oe and 304 kHz were measured using D5 hyperthermia system to be 126, 33 and 73 W/g for sizes of 63, 91, and 128 nm, respectively. The results yield efficient heating and the nanoparticles perfect feasibility for magnetic hyperthermia treatment of cancer. |
Friday, March 8, 2019 1:03PM - 1:15PM |
Y39.00010: Preparation and Investigation of Carbon Coated (Fe-Fe3C) Nanocomposites for Medical Applications Aram Manukyan, Harut Gyulasaryan, Eduard Sharoyan, Jennifer Gray Lynn, Oscar Bernal, Armen Kocharian Carbon-coated ferromagnetic (Fe-Fe3C) nanocomposites have been synthesized via solid-phase pyrolysis of metal-organic compaunds. Structure, morphology and magnetic characteristics of the nanocomposites were investigated by electron microscopy, X-ray diffraction, Raman spectroscopy, STEM-TEM images, EDX line-scan profiles and magnetometry. The magnetic characteristics such as saturation magnetization, coercivity and heating saturation as well as the specific absorption rate (SAR) make these materials attractive for magnetic hyperthermia applications. Hysteresis loop of the (Fe-Fe3C)@C nanocomposites is of special interest as it shows almost square-like behaviour, where Mr/M(200 Oe) = 0.75.The limitation of the magnetic field amplitude and - frequency (H x f) ≤ 10.625x106 Oe/s makes this factor important that provids a high energy absorbtion even in case of low magnetic fields. |
Friday, March 8, 2019 1:15PM - 1:27PM |
Y39.00011: Ultrathin cobalt nanowires with high energy product Meiying Xing, Jeotikanta Mohapatra, Jacob Elkins, Julian Beatty, J Ping Liu Uniform and single crystalline hexagonal close-packed (hcp) Co nanowires (NWs) have been synthesized by optimizing the precursor concentration and cleaning process in a hydrothermal process1. The TEM image indicates that the prepared Co NWs have uniform size distribution with a mean diameter and length of 8 nm and 150 nm, respectively. As the radius of the Co NWs is smaller than coherent radius Rcoh = 3.65 lex, where lex is the exchange length, the ultrathin Co NWs exhibit the coherent magnetization reversal based on the Stoner-Wohlfarth mode. As a result, a pronounced coercivity of 11.4 kOe is achieved in the aligned Co NW assemblies. The high aspect-ratio, good crystallinity, uniform morphology and desired orientation of Co NW assemblies result in a record high energy product of 56.1 MGOe which is close to the theoretical value. The compaction of the prealigned NWs assemblies at various pressure results in packing density in the range from 5.3 to 7.3 g/cm3 and energy product as high as 20 MGOe. The obtained nanowire based permanent magnets with well controlled aspect ratios exhibited energy products in the intermediate range between Alnico and rare-earth containing magnets. |
Friday, March 8, 2019 1:27PM - 1:39PM |
Y39.00012: Search for the new rare-earth free iron-based permanent magnets Olga Vekilova, Olle Eriksson, Heike C. Herper Permanent magnets are irreplaceable for many technological applications. Therefore new magnetic materials, that are cheap and abundant, are vital for the modern society. A good permanent magnet must have a high Curie temperature, high saturation magnetization and uniaxial magnetocrystilline anisotropy. Rare-earth free Fe-rich systems like the hexagonal close-packed Fe3Sn compound are promising candidates. However, its magnetocrystalline anisotropy is planar. Alloying is a possibility for changing the easy axis of magnetization. |
Friday, March 8, 2019 1:39PM - 1:51PM |
Y39.00013: High-Performance Thick On-chip Hard Magnets for MEMS Applications Yifan He, Chengju Yu, Samer Haider, Mohsen Zaeimbashi, Gregory Stephen, Jiawei Wang, Yuyi Wei, Huaihao Chen, Xianfeng Liang, Cheng Tu, Cunzheng Dong, Don Heiman, Baoxing Chen, Nian Xiang Sun We adopted two methods for thick on-chip hard magnets fabrication for MEMS application. (1) Dry packing of Nd2Fe14B powders. Nd2Fe14B powders were mixed with binder wax powders, then dry-packed into pre-etched trenches on silicon wafers under 10 MPa pressure and 100°C heating. An out-of-plane, in-situ magnetic field of 1000 Oe was applied during the process. (2) High pressure compression of Nd2Fe14B powders. Nd2Fe14B powders were packed into a metal mould and heated to 300°C with 850 MPa pressure applied. The sample was bonded onto the silicon chip with polyimide. The dry-packed Nd2Fe14B magnets showed a remanent out-of-plane magnetization of 330 emu/cc (Br = 0.42 T), a coercive field of 8.6 kOe (690 kA/m) and an energy product of 2.4~2.6 MGOe (19-21 kJ/m3). It is also found that the out-of-plane magnetic field can boost the remanent magnetization in that direction. For high pressure compressed Nd2Fe14B magnets, a remanent out-of-plane magnetization of 446 emu/cc (Br = 0.56 T), a coercive field of 9.6 kOe (770 kA/m) and an energy product of 6.4 MGOe (50.5 kJ/m3) were observed. Our demonstrated Nd2Fe14B on-chip hard magnets are compatible to MEMS fabrication process with a larger thickness of over 1mm and higher achieved energy product over published results for on-chip magnets. |
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