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    Design and Implementation of a High-Field NdFeB Magnet System for Investigating the Spin Seebeck Effect
    (2025-01-01)
    Nachaithong, Theeranuch
    ;
    Wongjom, Chalothon
    ;
    Samransuksamer, Benjarong
    ;
    Phumying, Santi
    ;
    Pongophas, Ekkarat
    The generation of pure spin current through thermal gradients, known as the spin Seebeck effect (SSE), has garnered significant interest in spintronics. In this study, we design and construct a permanent magnetic instrument setup to generate a variable external magnetic field using NdFeB permanent magnets to observe the SSE. The experimental setup is composed of three crucial components: the magnetic field, the temperature gradient, and electronic control systems. Si/yttrium iron garnet (YIG)/platinum (Pt) and Si/nickel (Ni) samples, prepared via sputtering techniques, were utilized for standard calibration purposes. The results show that the external magnetic field produced by NdFeB varies with the gap distance between the two magnetic poles, following an exponential decrease in field strength with increasing gap distance. The magnetic field at the center can be adjusted from ±20 to ±5000 Oe. The temperature gradient stabilizes after approximately 10 min, with a temperature difference ( ΔT ) between the heated and cooled sides ranging from 0 to 30 K. For instrument testing, we performed magnetic field and angle-dependent measurements on Si/YIG/Pt and Si/Ni samples. The results indicate that the magnetic field dependence of the permanent magnet instrument (PMI) does not exhibit the voltage loop switching seen with an alternative magnetic coil (AMC) but shows analogous behavior at high magnetic fields. Moreover, the angle dependence of both PMI and AMC yielded comparable results. In conclusion, our PMI setup procedures effectively facilitate the observation of the SSE.
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    Magnetization of NdFeB Permanent Magnet Considering Demagnetization Effect
    (2018-11-27)
    Sarikprueck, Piampoom
    ;
    Lumyong, Pichit
    ;
    Niroiana, Chamakorn Na
    ;
    Attaphong, Chodchanok
    Electrical machine efficiency improvement has been paid more attention over the past years. Using Permanent Magnets (PMs) in various modern electrical machines is one of the most favorable approaches to increase machine efficiency. However, PMs still have a significant disadvantage that is the demagnetization issue. Therefore, these demagnetized PMs need to magnetize for regaining their initial capability considering the demagnetization level. Therefore, first of all, this paper proposes the demagnetization behavior of NdFeB PMs due to thermal effect. Then, these PMs are magnetized using a proposed simple magnetizing technique considering various demagnetization conditions. Finally, the results indicate that the most complete demagnetized PMs are able to significantly recover to their initial capability.