Thông tin chung


  Đề tài NC khoa học
  Bài báo, báo cáo khoa học
  Hướng dẫn Sau đại học
  Sách và giáo trình
  Các học phần và môn giảng dạy
  Giải thưởng khoa học, Phát minh, sáng chế
  Khen thưởng
  Thông tin khác

  Tài liệu tham khảo

  Hiệu chỉnh

Số người truy cập: 103,456,956

 Magnetization Measurement System With Giant Magnetoresistance Zero-Field Detector.
Tác giả hoặc Nhóm tác giả: Van-Dong Doan, Jen-Tzong Jeng*, Huu-Thang Nguyen, Chinh-Hieu Dinh, Duy Vinh Dao, Thi-Trang Pham
Nơi đăng: IEEE - The International Magnetics Conference (INTERMAG 2021); Số: CR-09;Từ->đến trang: 579;Năm: 2021
Lĩnh vực: Kỹ thuật; Loại: Báo cáo; Thể loại: Quốc tế
Magnetic hysteresis loop measurement [1]-[4] is crucial for the development
of advanced magnetic materials. From the magnetization versus magnetizing
field (M-H) curve, one can extract the useful magnetic properties, which are
important for applications in sensors, transformers, actuators, and miscellaneous electrical devices. The M-H measurements were usually done by using
the vibrating sample magnetometer [1] or the SQUID magnetometer [2], for
which the magnetizing field are virtually static during the measurement. The
induction-coil-based hysteresis loop and susceptibility measurement systems
[3], [4] are rapid and low-cost devices capable of determining the alternating-current (AC) magnetic properties, which is important for inferring the
frequency-dependent features such as the energy loss due to eddy currents in
conducting materials. The convention hysteresis loop measurement device
[3] is designed for the magnetic induction versus field (B-H) measurement
of toroidal samples. The alternating susceptibility measurement system (AC
susceptometer) is capable of determining the frequency dependent initial
magnetization and susceptibility. But the induction coil can’t detect the environmental direct-current (DC) field. For the soft magnetic materials, the
non-zero environmental magnetic field can significantly alter the measured
result, which must be compensated by using a magnetic sensor to detect
the unwanted magnetic interference. To achieve higher accuracy in the
M-H measurement, we proposed a M-H measurement system combining
the signal processing method of B-H measurement and the coil design of
the AC susceptometer. The interference from the environmental magnetic
field is eliminated by using a giant magnetoresistance (GMR) sensor as the
zero field detector, as shown in Fig. 1. The system consists of solenoidal
magnetization and pickup coils. The pickup coil consists of reference and
sensing coils symmetrically positioned with respect to the excitation coil.
The sensing coil detects the magnetization of the sample, whereas the reference coil is wound in the opposite direction to null out the magnetizing
signal. The signal output of the integrator is proportional to the magnetization of the sample. The current in the magnetization coil is directly proportional to the magnetizing field strength H. However, the DC level of the
magnetizing field at the sample is usually shifted by the environmental field,
which can’t be observed by monitoring the current in the coil. To solve the
problem, the GMR sensor, which is the GF708 spin-valve sensor [5] from
Sensitec GmbH, is used for the zero field detector. The sensor has a very
high sensitivity but the dynamic range less than 2 Oe. The output of GMR
is used as the trigger for taking the M-H curve to eliminate the disturbance
from the environmental DC field, as shown in Fig. 2. The 1-Hz sinusoidal
current signal measured by a resistor shows a peak-to-peak amplitude of
0.96 A, corresponding the magnetizing field amplitude of 6.7 mT. When the
environmental DC field was completely eliminated in the pickup coil, the
observed output signal of the GMR has a zero-field-crossing point defined
by the trigger level, shown as in Fig. 2. The trigger point to activate the M-H
measurement is at the intersection of the trigger level line and the GMR
signal curve for “No external field”. When the DC field (of about 0.77 mT)
was applied, the trigger point shifted by 40 ms in comparison with the zerofield curve, while the current waveform in the coil remained unchanged.
The new trigger point to activate the M-H measurement is at the intersection
between the trigger level line and the GMR signal curve with “External
field”. The coercivity and the asymmetry pinning field of the GMR sensor
induces a constant time shift in the trigger point, which can be corrected by
employing a calibration procedure provided that the sweeping magnetizing
field always saturates the output of GMR on both field polarities. With the
GMR zero-field detector to set the trigger point, the high-quality M-H curve
can be obtained by taking averaging for multiple cycles of the sweeping
magnetizing field. In this way, the accuracy of the M-H curve measurement
for the soft magnetic materials is successfully improved by eliminating the
interference from the environmental field without using a costly magnetic
shield chamber.
© Đại học Đà Nẵng
Địa chỉ: 41 Lê Duẩn Thành phố Đà Nẵng
Điện thoại: (84) 0236 3822 041 ; Email: