Somphonsane, Ratchanok

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Preferred name
Somphonsane, Ratchanok
Alternative Name
Somphonsane, R.
Main Affiliation
Email
ratchanok.so@kmitl.ac.th

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    Spin Seebeck effect and large spin conversion in amorphous Fe2TiSb/polycrystalline Y3Fe5O12 thin films
    (2024-05-30)
    Wongjom, Poramed
    ;
    Wongjom, Chalothon
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    Pongophas, Ekkarat
    ;
    Infahsaeng, Yingyot
    ;
    Maiaugree, Wasan
    This study investigates spin current generation in a Fe<inf>2</inf>TiSb/Y<inf>3</inf>Fe<inf>5</inf>O<inf>12</inf> multi-layer thin film as prepared via the magnetron sputtering method. Comprehensive characterization techniques are employed to assess film properties, including X-ray diffraction, energy-dispersive X-ray spectroscopy, Scanning electron microscopy, and Vibrating sample magnetometer. The Y<inf>3</inf>Fe<inf>5</inf>O<inf>12</inf> material exhibits a polycrystalline ferromagnetic insulator behavior, while the 20 nm-thick Fe<inf>2</inf>TiSb film displays small ferromagnetic metal properties with an amorphous structure. Spin current analysis utilizes the longitudinal spin Seebeck effect configuration, considering magnetic field and temperature dependencies and the results show that spin conversion within the Fe<inf>2</inf>TiSb/Y<inf>3</inf>Fe<inf>5</inf>O<inf>12</inf> structure is influenced by both the spin Seebeck effect and the anomalous Nernst effect, resulting in an overall spin signal enhancement. The spin Seebeck coefficient of Fe<inf>2</inf>TiSb/Y<inf>3</inf>Fe<inf>5</inf>O<inf>12</inf> was approximately 0.103 μV/K within a magnetic field of 300 mT.
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    Investigating the shunting effect in a Fe/Co ferromagnetic metal hybrid structure and its impact on the spin Seebeck effect
    (2024-03-01)
    Phumying, Santi
    ;
    Wongjom, Chalothon
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    Pongophas, Ekkarat
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    Infahsaeng, Yingyot
    ;
    Maiaugree, Wasan
    The generation of spin voltage by heat, known as the spin Seebeck effect (SSE), involves the injection of spin current from a ferromagnetic to a normal metal. In this study, the shunting effect in SSE is investigated within a hybrid structure consisting of iron (Fe) and cobalt (Co) films deposited on a Si-wafer substrate using thermal evaporation [Si/Fe(500 nm)/Co(10 nm)]. Spin voltage measurements performed in the in-plane configuration revealed a voltage reversal in the Co film and Fe film. However, in the hybrid structure (Si/Fe/Co), the voltage signal exhibited consistent directionality. This intriguing observation hints at a potential shunting effect, wherein the voltage influence from the Fe layer contributes to the Co film. Consequently, it is deduced that a significant shunting effect occurs when the resistivity of Fe is approximately three orders of magnitude lower than that of the Co film. This insight sheds light on the intricate dynamics of spin thermoelectric applications, emphasizing the role of material properties in optimizing performance.
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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
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    Wongjom, Chalothon
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    Samransuksamer, Benjarong
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    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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    Low-Cost Instrument for the Versatile Measurement of Spin Caloritronic Phenomena: Spin Seebeck Effect, Anisotropic Magnetoresistance, Anomalous Hall Effect, and Anomalous Nernst Effect
    (2023-01-01)
    Pongophas, Ekkarat
    ;
    Infahsaeng, Yingyot
    ;
    Maiaugree, Wasan
    ;
    Phumying, Santi
    ;
    Pattanakul, Rungrueang
    In this article, we report on a low-cost instrument for the versatile measurement of spin caloritronics phenomena such as the spin Seebeck effect (SSE), anomalous Nernst effect (ANE) anisotropic magnetoresistance (AMR), and anomalous Hall effect (AHE). Solenoid coils provide a uniform variable magnetic field while the sample was sandwiched between thermal baths and measured in a vacuum chamber. Our results show excellent magnetic field uniformity (±0.37 mT) within the magnet gap and high stability of the generated temperature difference (±0.07 K). For verifying the effectiveness of our instrument, Yttrium Iron garnet (YIG)/Co structure was used to measure the SSE, AMR, and AHE, while a SiO2/Co structure was used for measuring the ANE. Our SSE measurements of the YIG/Co structure were found to be comparable with that of a commercially available instrument. We can therefore conclude that our low-cost and versatile instrument can be used to effectively observe spin Caloritronics phenomena.
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    The Spin Voltage Enhancement in Si/YIG/Co, Fe Spin Hall Thermopiles
    (2024-01-01)
    Kumpor, Wimutti
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    Kuptapol, Perawas
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    Wongjom, Chalothon
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    Pongophas, Ekkarat
    ;
    Infahsaeng, Yingyot
    Spin-Hall thermopiles have been previously proposed as a means to enhance the spin Seebeck effect (SSE). However, the use of platinum (Pt) for spin detection drives costs high and proves an impediment for scalability. In this work, a cost-effective spin-Hall thermopile constructed from opposite spin-Hall angle ferromagnets, cobalt (Co) and iron (Fe), is reported. The devices are fabricated using a standard sputter-coated yttrium iron garnet (YIG) substrate that serves as the spin injector, and thermally evaporated Co and Fe strips that enable spin detection. When serially connected to form a (YIG/Co, Fe) thermopile structure, measurements indicate a significant enhancement of the spin voltage that results from the additive spin contributions of the opposite spin-Hall angle ferromagnets and the anomalous Nernst effect (ANE) that they exhibit. The YIG/Co, Fe thermopile reported here offers a cost-effective alternative to Pt-based thermopiles and the possibility of large-scale implementation to realize future thermoelectric generators.