United States

Interfacial Dzyaloshinskii-Moriya interaction (iDMI) [1,2] along with perpendicular magnetic anisotropy (PMA) [3,4] in the ultrathin ferromagnetic material/heavy metal (FM/HM) interface has garnered significant attention in recent studies [5,6]. Field-induced domain wall motion has been observed in quasi-perpendicularly magnetized Pt/Co/Pt trilayers with interfacial Dzyaloshinskii-Moriya interaction (iDMI) using differential Kerr microscopy method in the creep regime (shown in Fig.1). Vineeth et al. [7] reported a quasi-PMA system whose magnetic easy axis is tilted with respect to the z-axis. An oblique angle sputter deposition technique had introduced a thickness gradient in one of the layers of a trilayer, results in a small tilt of magnetic anisotropy from the film normal. The tilt angle has been estimated in each trilayer by determining the shift in the out-of-plane magnetization hysteresis measurements under a bias magnetic field applied along with various in-plane directions. The effective in-plane field at the domain wall due to iDMI has been determined by decomposing the symmetric and asymmetric contributions of the domain wall motion. Furthermore, the asymmetric contribution has been decomposed into two contributions due to the tilted magnetic anisotropy and the exponentially decaying chiral damping. The nature of the asymmetric contribution owing to the tilted anisotropy was studied by the collective coordinate model (shown in Fig.2) and a functional form of the total asymmetric contribution has been determined and used to fit the asymmetric contribution [8].

![](https://assets.underline.io/uploads/markdown_image/1/image/5efdf9ff8cc28df94d0815f6a78b3176.jpg)

Fig.1: Field-induced domain wall motion for all the trilayers obtained using differential polar Kerr microscopy technique. Corresponding applied Hx and pulsed Hz with the pulse-width Δt are mentioned under the images. Azimuthal orientation of the tilted magnetic anisotropy has been shown using a white arrow for each trilayer.

![](https://assets.underline.io/uploads/markdown_image/1/image/41d857e809588a526d2249dfb541c16a.jpg)

Fig.2: Dependence of asymmetric contribution, Ha on Hz have been shown for azimuthal orientation along the x-axis for all the trilayers. All the solid lines through the data points validate the CCM.



2022 Joint MMM-INTERMAG

Asymmetric magnetic domain wall motion in a quasi-perpendicularly magnetized with interfacial Dzyaloshinskii-Moriya interaction

## Dr. Nishikant (Nish) Sonwalkar: Academician, Scientist, Musician

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Dr. Sonwalkar is regarded as a leading expert in the application of computers in education. He has extensive research and development experience in hypermedia authoring, mobile learning, adaptive learning, and brain-based synaptic learning, advanced scientific visualization, database management systems, and computer simulation.

After receiving doctoral degree from MIT in the area of Molecular Dynamics of Nano-interfaces, he joined MIT as faculty in Mechanical Engineering, but his passion for technology enabled education led him become the founding director of Hypermedia Teaching Facility (Hypermedia Lab) at MIT and later he was appointed as the Principal Educational Architect of MIT.

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NISH 2021

poster

The 15th Joint MMM-INTERMAG Conference (2022 Joint) is sponsored jointly by AIP Publishing and the IEEE Magnetics Society. Members of the international scientific and engineering communities interested in recent developments in fundamental and applied magnetism are invited to attend and contribute to the technical sessions. The technical program will include invited and contributed papers in oral and poster sessions, invited symposia, a plenary session, and an evening session, with about 1500 presentations overall. This Conference provides an outstanding opportunity for worldwide participants to meet their colleagues and collaborators and discuss developments in all areas of magnetism research.

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Introduction It is very important to inspect the shrinkage cavity inside the cast iron, since the spheroidal graphite cast iron (FCD600) may be generated a shrinkage cavity inside it during manufacturing and the strength is extremely reduced. In this research, a new inspection method using differential vibration measurement by electromagnetic force excitation is proposed. In this method, the vibration by the electromagnetic force is generated from the static magnetic field of the permanent magnet and the eddy current inside the cast iron by the alternating excitation coil. Then, the shrinkage cavity is evaluated using the vibration strength of the cast iron surface. In this paper, 3D electromagnetic field analysis and 3D displacement analysis [1] are used to elucidate the test principle and to conduct verification experiments. Inspection Model and Conditions Fig.1 shows the proposed sensor is composed of a permanent magnet with two holes, an AC exciting coil with 500Hz and 2A, and two vibration sensors. The electromagnetic vibration is generated in the steel plate by the static flux density from the permanent magnet and the eddy current from the excitation coil. And, two vibration sensors are measured the vibration strength of the steel plate surface differentially. The shrinkage cavity inside cast iron is estimated by the differential vibration intensity. Calculated and Inspection Results Fig.2(a) shows that the calculated distribution of differential displacements by the two vibration sensors at each position on the cast iron. This figure denotes that the displacement distribution is changed near the shrinkage cavity inside the cast iron. This is because, the density in the cast iron is decreased near the shrinkage cavity in the cast iron. (3) shows the measured differential signal of two vibration sensors at each position on the actual cast iron with the shrinkage cavity. This figure denotes that the differential signal is changed near the shrinkage cavity in the cast iron. Moreover, the measured signal is a tendency similar to the calculated result as shown in Fig.2. The presence of shrinkage cavity inside the cast iron can be confirmed by this change in the differential signal.

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Proposal of Inspection Method for Shrinkage Cavity in Spheroidal Graphite Cast Iron Using Differential Vibration Measurement by Electromagnetic Force Vibration

In many applications including space missions, Anisotropic Magnetoresistors (AMR) based magnetometers raised their popularity [1,2] as they are solid-state off-the-shelf components with good radiation immunity [3]. One of the issues they suffer is low sensitivity and thus high noise induced by their bridge thermal noise as well as by preamplifier stage noise [4]. To overcome this problem, higher supply voltage of an AMR bridge can be used to raise the sensitivity. This seems to be straightforward but power dissipated on the sensor raises quadratically with bridge voltage and thus it can’t be operated in "classical" continuous mode (due to overheating and excessive power consumption). In our research we propose novel method of powering bridge by pulses allowing to obtain better sensitivity and less noise with AMR sensors. During these short pulses (100 us width and 4.5 ms period) we also perform flipping pulses (both S/R) while measuring bridge response with an analog-to-digital converter. Acquired data are then signal-processed on the fly by a microcontroller. In traditional method, 10 V in continuous mode with HMC1021 AMR sensor will dissipate 91 mW of power, while cycling power with a duty cycle of 1:45 means only 2 mW (considering zero overhead power). In mostly used triaxial version it is 273 mW vs 6 mW preserving other main parameters of the magnetometer unchanged. To verify this idea we have developed single axis magnetometer (Fig. 1) with adjustable both bridge voltage as well as flipping current, with possibility of precise timing of all events. In the first trial/test, we have tried to obtain similar noise with pulsed 10 V bridge as we were able to get in our previous research with continuous supply of 10V [4], (see Fig 2.) After achieving this milestone (solving a lot of technical troubles) we tried 20 V bridge supply to verify expected noise reduction (as sensitivity doubles), but for now without result – at this voltage, AMR's electrical offset saturates the preamplifier. In the near future we aim to tackle this issue and to test the noise drift with temperature in different flipping current configurations.

![](https://assets.underline.io/uploads/markdown_image/1/image/f21d8768f1f6f2a671e16af4a0ec4b66.jpg)

Fig.1 - Photo of the experimental prototype

![](https://assets.underline.io/uploads/markdown_image/1/image/56f845d2e47285017dd6de7e45a96175.jpg)

Fig.2 - PSD of noise with pulsed 10 V bridge voltage

Low-Power AMR Magnetometer Operated in Discontinuous Mode

1.Study Objective and Method Transformer magneto-mechanical structure deformation due to lightning impulse effect may cause damage of the transformers in terms of the noise and vibration performance. This study proposed a single-phase transformer with a voltage specification of 345 kV (high voltage)/115 kV (low voltage) and a capacity of 120 MVA [1,2]. The results of the continuous lightning impulse tests revealed that the transformer designed as parameter of K-factor, as shown in Figure 1. After testing results, there is generated significantly low noise (&lt;65 dB) and vibration (&lt;10 μm), which are remarkably lower than the IEEE standard of 85 dB. 2.Experiment Result and Discussion The pattern of the fault currents depends on the fault type and location along the winding length. Figure 2(a)-(b) shows the transformer after the lightning impulse full-wave and chopped wave for high voltage bushing level. The Figure 2(c) shows the thermal imaging results of the transformer after the lightning impulse testing, indicating that high (102 °C) and low (31.2 °C) thermal conduction were obtained at the two sides of the top collier. These thermal imaging measurement results suggest that the transformer can operate effectively because it exhibits satisfactory insulation performance after the lightning impulse and alternating current insulation tests [3,4]. The sweep frequency response analysis is a useful method to detect and diagnosis of the defects for the power transformers. The results of the frequency spectral tests are conducted using SFRA are shown in Figure 2(d). Based on the SFRA theory, the core properties affect the SFRA characteristics only at low frequencies (typically up to 1 kHz). Therefore, the noise results can be considered as correction values between the values obtained before and after the application of the SFRA. The k-factor between 0.4-0.6 for transformer insulation is maintained better performance.

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Figure 1 Lightning k-factor: (a) turn-to-turn insulation and overshoot voltage, (b) k-factor distribution.

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Figure 2. Lightning impulse results: (a)-(b) full wave voltage and current, (c) thermal imaging, front-back side, (d) SFRA at 10 Hz–2 MHz before and after the lightning impulse test.

Effects of the Electromagnetic Structure of the Power Transformer Core on Hysteresis Squareness Ratio, Noise and Vibration Characteristics

Studies have shown that relaxing music can lower a patient’s breathing rate, heart rate, and blood pressure by releasing stress or anxiety and promoting relaxation [1,2]. Based on the successful development of our magnetic respiratory monitoring technology for advanced healthcare [3], in this study we attempt to examine how the breathing pattern of a patient changes when the patient sleeps with and without a favorite music in the background. We observed that during sleep mode with music, the patient breathed more regularly and slowly (11 times per minute) compared to sleep without music (14 times per minute) and wake mode (17 times per minute). This indicated that the relaxing music helped the patient to relax and sleep better. Remarkably, while the abnormal breathing feature was observed at a certain time for all states (wake-up and sleep modes with and without music), the breathing pattern became more regular in the case of sleep with the relaxing music. Furthermore, we designed a musical biofeedback for breathing regulation. In this design, the respiratory motion of the patient was tracked and interpreted as a real-time variable for tempo adjustment to a stored musical file. The patient was able to adjust breathing to synchronize with a separate accompaniment line. When the breathing was regular and at the desired tempo, the resulting sound was synchronous and harmonious. These observations suggest a new possibility of integrating our magnetic respiratory monitoring technology with music to develop an innovative magnetic music therapy for Covid19 patients with breathing difficulty.

Magnetic Respiratory Monitoring Technology Based Music Therapy for Covid19 Patients: A New Perspective

Inductance and resistance of a coil are important parameters for electromagnetic sensors and actuators. If the sensors or actuators are to be operated in high temperature environments, the effect of temperature change on inductance and resistance must be evaluated [1-2]. In this paper, we propose a very simple procedure for estimating the inductance and resistance of toroidal coils operating in high temperature environment. Magnetic stainless steel (SUS430) is used as the core. The ring is wound with ceramic-coated cable. The test specimen is placed inside an oven in which the temperature is controlled up to 500°C. The winding is driven by a linear amplifier (TA330, TRUST Automation) at the command of a function generator (33120A, Agilent). The current is measured by a current probe (80i-110s, Fluke). Fig. 1 illustrates the test setup and shows a picture of the test specimen in the oven. The current through the coil is related to the applied voltage through V = L (di/dt) + Ri. Transfer function between the voltage and current can be obtained as G = 1/(Ls + R). Introducing a new operator λ=1/(1+τs), we can set up a time-domain identification scheme [3]. The inductance and resistance can be estimated through the following recursive least square estimation algorithm. Defining the parameter vector theta = [ L R ], (1) θ(k) = θ(k-1)+P(k)φ(k)e(k) (2) e(k) = y(k) - φ(k)θ(k-1) (3) P(k) = P(k-1) - P(k-1)φ(k)φ(k)P(k-1)/(1+φ(k)P(k-1)φ(k)) The parameter τ determines the convergence speed. In order to validate the method, the resistance of the coil is measured using a precision multimeter (34401A, Agilent) and the inductance is measured with an LCR meter (4263B, Agilent). Fig. 2(a) shows the estimation results compared with the measurements. Fig. 2(b) displays the comparison of resistance estimation with measurements. The estimation for inductance is better than the resistance in terms of agreement with measurements. Since the estimation model is the first order, it is not possible to obtain good estimation quality both for inductance and resistance. Since the resistance is stationary, it may be possible to have another procedure to estimate the resistance, thereby enhancing the quality. This work is supported by National Research Foundation of Korea (NRF-2020R1F1A1067740)

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Estimation of inductance and resistance of toroidal coils in high temperature environment

Estimation of inductance and resistance of toroidal coils in high temperature environment

Various industrial applications have put forward higher demands for wireless power transfer systems (WPT) [1]. Using one transmitter to simultaneously power multiple appliances with different electrical requirements is a promising system with the advantages of simplicity and good efficiency [1-2]. One of the key issues of multifrequency transmission is the power adaption and power flow control [3-5]. Most of the traditional work uses the modulation method to solve this problem. However, the signal tracking process can be difficult and complex and will inevitably cause more power losses [2], especially for high operation frequencies. This paper presents a new design scheme to realize the power adaption for multiple receivers. The system can realize a demand-customized output power by adjusting the current harmonics. The system uses only one simple full-bridge inverter, and the redundant modulation process can be cut away. As shown in Fig. 1, the proposed compensation circuit uses a T-type topology. Each branch of the circuit is made of a dual-band component. Based on superposition method, the output voltage of the inverter can be regarded as the combination of the first and third harmonics. Under each operation frequency, the three dual-band components can behave different equivalent impedances and the compensation circuit can thus be regarded as two individual LCC compensation for the accordant frequencies, which guarantees that the system can always operate at zero impedance angle and with adjustable output current harmonics. The simulated operating waveforms of the proposed system are shown in Fig. 2. For two identical resistive loads, the accordant receivers are designed to be resonant at 100 kHz and 300 kHz, respectively. The first and third harmonics of the input current are thus designed to be 3:1 for equivalent output. It can be observed that the compensation circuit successfully controls the output current to the desired values with the inherent harmonics of the input voltage. This work was supported by HK RGC (project no. T23-701/20-R).

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Power Adaption Design for Multifrequency Wireless Power Transfer System

Power Adaption Design for Multifrequency Wireless Power Transfer System

Introduction It is important to detect corrosion or defects on the opposite side of steel walls used for structures in petrochemical plants. In this research, the detection method of the opposite side defect in the steel plate by applying vibration due to electromagnetic force and measuring its vibration is proposed. The proposed sensor probe consists of a permanent magnet, an AC excitation coil and a vibration sensor. The defect is evaluated by the excitation frequency component of the measured the vibration intensity. The vibration distribution by the electromagnetic force in the steel plate with and without the defect is evaluated by the electromagnetic nonlinear 3D-FEM and the displacement 3D-FEM analysis. In addition, the verification experiment is also carried out. Inspection model and conditions Fig. 1 shows a proposed sensor using an AC magnetic field of 2A at 700Hz. The alternating current of 700Hz and 2A is passed to the exciting coil. In the proposed sensor, the electromagnetic vibration inside the steel plate is generated by the eddy current from an exciting coil and static flux density from the permanent magnet. Then, a ceramic bar is connected to the vibration sensor, and the vibration on the surface the steel plate is measured. Inspection result and discussions Fig.2 shows the distribution of the displacement at each position on the steel plate when the proposed sensor is moved in the x-direction. Fig.2 (a) shows the calculated results, and Fig.2 (b) shows the measured results, respectively. Fig.2 (a) shows the calculated displacement distribution of the vibration sensor inside the proposed sensor by 3D displacement analysis and 3D electromagnetic nonlinear analysis. This figure denotes that the displacement is increased near the defect in the steel plate. This is because, the density of the steel plate is decreased near the defect. Fig. 2(b) denotes that the detection signal is increased near the defect, similar to the analysis result of Fig.2 (a). From these results, the opposite side defect in the steel plate is detected by the vibration intensity of the steady frequency.

![](https://assets.underline.io/uploads/markdown_image/1/image/81f55cc0ea115021b4f77fa775f55330.jpg)

Proposed sensor and Inspection model

![](https://assets.underline.io/uploads/markdown_image/1/image/c0296a6704b129d5622293ae1f645b74.jpg)

Comparison of analysis results and experimental results

Proposal of inspection method for opposite side defect in steel plate using electromagnetic force vibration

Introduction It is important to detect an opposite side defect in steel wall in petrochemical plants. As the inspection for the defect, the electromagnetic inspection method using static and alternating magnetic field is examined [1]. However, this method is required two types of power supplies of static and alternating current. On the other hand, when the full-wave rectified magnetic field is expanded by fourier series, it is the combined magnetic field of static and alternating magnetic field. Therefore, in this paper, the inspection method by the full-wave rectified magnetic field using only one power supply is investigated. Since the magnetic property inside the steel plate in this method is minor loop, the flux density is analyzed by 3D nonlinear FEM using the “play model [2]” taking account of minor loop magnetization property. In this research, the usefulness of the inspection method is evaluated by the “play model” and verification experiment. Inspection model and results Fig.1 shows an inspection model using 2 kHz and 1A at a full-wave rectified exciting current. Although the full-wave rectified magnetic field is an AC magnetic field, the flux density is penetrated deep into the steel plate. If there is an opposite side defect, the flux density is distributed around the defect, and leakage flux is generated on the surface of the steel plate. The defect is evaluated by detecting this leakage flux. Fig.2 shows the comparison between calculated and measured results of the detection signal. The vertical axis is the rate of change ηd with respect to the presence or absence of defect in the output voltage, and the horizontal axis is the moving position of the sensor. This figure denotes that the detection signal is increased at the center position of the defect. And, the calculated result is also same tendency as measured result. The inspection of the opposite side defect in the steel plate is possible by impressed the full-wave rectified magnetic field.

![](https://assets.underline.io/uploads/markdown_image/1/image/41552b283ec6eeda7685f2cc051f4bc5.jpg)

Proposed inspection model using full-wave rectified magnetic field(1/2 model).

![](https://assets.underline.io/uploads/markdown_image/1/image/40796d4744f1a8945c2d416adf7650d1.jpg)

Detection signals of the opposite side defect in the steel plate using the full-wave rectified magnetic field (2kHz, 1A0-p).

Examination of electromagnetic inspection method for opposite side defect on steel plate using full-wave rectified alternating magnetic field

Hybrid magnonic systems host a variety of characteristic quantum phenomena such as the magnetically-induced transparency (MIT) and Purcell effect, which are considered useful for future coherent quantum information processing [1-2]. Here, we experimentally demonstrate a tunable MIT effect in the YIG/Py magnon-magnon coupled system via changing the magnetic field orientations. By probing the magneto-optical Kerr and Faraday effects of Py and YIG, we identify clear features of MIT spectra induced by the mode hybridization between the ferromagnetic resonance of Py and the perpendicular standing spin-wave of YIG. By changing the external magnetic field orientation, we observe a tunable coupling strength between the YIG's spin-wave modes and the Py's uniform mode, upon the application of an out-of-plane magnetic field. Our findings show high promise for investigating tunable coherent phenomena with hybrid magnonic platforms.

Facile Magneto-optic Detection of Tunable Magnetically-Induced Transparency Spectra in Magnon-Magnon Coupled Bilayers

The imaging of magnetic nanoparticle (MNP) distributions is a promising biomedical imaging technique for detecting cancers [1]. A method is magnetic nanoparticle tomography (MNT), in which multiple magnetic sensors are used to detect the harmonic signal of MNPs [2] [3]. In our previous study [2] [3], a linear amplifier power supply with low power efficiency was used to generate the excitation magnetic field. In this study, a square-wave inverter was alternatively used to provide high efficiency. However, the third harmonic excitation field was generated by the general square-wave inverter excitation, degrading the imaging performance. Therefore, we developed a method to suppress the third harmonic by shifting the switching phase of the inverter. The experimental setup is shown in Fig. 1. A full-bridge inverter was used to generate a square excitation voltage. Generally, a square-wave voltage was generated by shifting the switching phase of the left- and right-arms by 180°. The square voltage generated using this method contained the third harmonic. We developed a method to suppress the third harmonic by shifting the switching phase by 120°. In this case, the third harmonic does not appear theoretically. The Resovist MNP sample (500 mg-Fe / 150 mg) was arranged and magnetized by an alternating-current magnetic field in the Z-axis using an excitation coil. The sample moved on the x-y plane, and the third harmonic signal of the MNPs was obtained using 16 detection coils. The distance between the excitation coil and the sample was set to 35 mm. Figs. 2(a) and (b) show the third harmonic signal distribution from MNPs using 180° and 120° shifts, respectively, detected by a detection coil. The signal from the MNPs was masked by the excitation field noise (Fig. 2(a)). In contrast, the peak and trough were visible. The results show that the proposed method increases the feasibility of MNT using a square wave inverter excitation. This study was supported by the Japan Society for the Promotion of Science (JSPS) KAKENHI (Grant Number JP21H01342).

![](https://assets.underline.io/uploads/markdown_image/1/image/777fa0726302b15db535960bf43377e8.jpg)

Fig.1. Experimental setup

![](https://assets.underline.io/uploads/markdown_image/1/image/885c75975b872192e473feafc18347b4.jpg)

Fig. 2. Third harmonic signal distributions of MNPs using (a) 180° and (b) 120° shifts (The cross mark indicates the position of a detection coil.)

Asymmetric magnetic domain wall motion in a quasi-perpendicularly magnetized with interfacial Dzyaloshinskii-Moriya interaction

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Proposal of Inspection Method for Shrinkage Cavity in Spheroidal Graphite Cast Iron Using Differential Vibration Measurement by Electromagnetic Force Vibration

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