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- 저자 : Patil Deepak Rajaram (검색결과 5 건)
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Deepak Rajaram Patil,이쉥차이,김준희,남중희,조정호,김병익,김기훈 한국물리학회 2017 Current Applied Physics Vol.17 No.8
With increasing demands toward device miniaturization, Pb-free magnetoelectric laminates (MELs) with a small lateral dimension of ~3 3 mm2 have been synthesized by the tape-casting method. The MELs are composed of alternating layers of magnetostrictive NiFe2O4 and piezoelectric BaTiO3 with a uniform single layer thickness of t ¼ 50 and 15 mm, respectively. Both laminates exhibit much larger longitudinal ME voltage coefficient aE33 than the transverse ME voltage coefficient aE31 at both off-resonant and resonant frequencies, which is attributed to the preferential easy-plane alignment of the magnetic moments. Furthermore, enhancement in aE33 by more than 5 times has been achieved upon decreasing t from 50 to 15 mm in both resonance and off-resonance conditions. The enhanced aE33 values indicate that nearly ideal interface coupling between the ferromagnetic and piezoelectric layers is realized in the miniaturized, thinner MEL, pointing to practical application potential towards developing massproduced, low-cost ME devices.
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Enhanced magnetoelectric coupling in stretch-induced shear mode magnetoelectric composites
Patil Deepak Rajaram,Park Sung Hoon,Patil Seema,Kumar Ajeet,Ryu Jungho 한국세라믹학회 2021 한국세라믹학회지 Vol.58 No.6
Magnetoelectric (ME) laminates consisting of Pb(Mg 1/3 Nb 2/3 )O 3 -PbTiO 3 (PMN-PT)-based single crystals have recently attracted significant interest owing to their excellent piezoelectric properties. Particularly, ME laminates with d 15 -mode single crystals exhibit the strongest ME coupling, but the fabrication of ME laminates with 15 shear modes is challenging. Herein, we propose the generation of a stretch–shear mode ( d 15 -mode) by clamping the opposite ends of the top and bottom magnetostrictive layers in symmetric ME laminates. Two diff erent shear-stress-induced ME laminates were fabricated using Metglas/Galfenol as magnetostrictive layer, and 15-PMN-PZT as a piezoelectric layer. The ME laminates were studied under two different conditions, unclamped and clamped. Under unclamped condition, Galfenol/15-PMN-PZT/Galfenol (Metglas/15- PMN-PZT/Metglas) laminate showed maximum α ME value of 1.71 V/cm∙Oe (0.62 V/cm∙Oe), while under clamped condition, Galfenol/ d 15 -PMN-PZT/Galfenol (Metglas/15-PMN-PZT/Metglas) laminate exhibited an enhanced α ME value of 2.40 V/ cm∙Oe (0.87 V/cm∙Oe), indicating successful generation of the stretch–shear mode. Under clamped condition, α ME was enhanced by 140% compared with the that of the unclamped case, suggesting a 40% (0.25 V/cm∙Oe) contribution from the pure shear ME voltage coefficient along with the longitudinal extension contribution.
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Patil Deepak Rajaram,Park Sung Hoon,Hwang G.-T.,Ryu Jungho 한국세라믹학회 2022 한국세라믹학회지 Vol.59 No.3
Piezoelectric coefficients dij and gij, the key parameters of the piezoelectric constituent of magnetoelectric (ME) composites, strongly influence their ME coupling. Considering this fact, we adopted three different types of piezoelectric materials with different crystallographic orientations, namely, 31-, 32-, and 15-mode PMN-PZT single crystals, to fabricate ME laminates. ME laminates can be easily fabricated using 31- and 32-mode PMN-PZT crystals, but it is difficult to fabricate them using 15-mode PMN-PZT because of the challenges in generating the 15-shear mode. In this study, 15-shear mode ME laminates were fabricated by sandwiching 15-mode PMN-PZT single crystals between Metglas and Ni, both of which exerted opposing magnetostrictive stresses on the 15-mode PMN-PZT to generate two-sided shear vibrations in it. Prior to the fabrication, the number of Metglas layers was optimized, owing to its differing thickness from that of Ni, to generate equal magnetostriction at the same applied DC magnetic field. ME laminates fabricated using two-layer (2L) and three-layer (3L) Metglas exhibited a maximum ME voltage coefficient (αME) of 0.04 V/cm Oe. In contrast, the αME values of ME laminates fabricated using 31- and 32-mode PMN-PZT single crystals were 0.46 V/cm Oe and 1.45 V/cm Oe, respectively, much higher than that of the 15-mode ME laminate. The small ME coupling in the 15-mode ME composite can be attributed to the unideal shear mode generated in the ME laminate.
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Kumar Ajeet,Lee Geon,Thakre Atul,Patil Deepak Rajaram,Han Guifang,Ryu Jungho 한국세라믹학회 2023 한국세라믹학회지 Vol.60 No.6
This study reports the fabrication of manganese (Mn) doped antiferroelectric (AFE) thick fi lms (thickness of ~ 2 μm) of (Pb0.93 La0.07 )(Zr0.82 Ti0.18 )O3 (PLZT 7/82/18) at room temperature using aerosol deposition (AD) technique without any additional thermal treatment. The Mn-doped PLZT 7/82/18 AD thick fi lms demonstrate excellent energy storage and electrical properties despite being fabricated at room temperature. The dielectric properties of the PLZT AD thick fi lms were investigated across a frequency range of 100 Hz–1 MHz and a temperature range of 25–250 o C. The Mn-doped PLZT AD thick fi lms exhibit a dielectric constant of ~ 108, low dielectric loss of 0.0211, and high-temperature stability of ~ 5.5% (from 1 kHz to 1 MHz). The bipolar P-E and I-E hysteresis loops of the PLZT AD thick fi lms do not show an AFE behavior, however, resemble the paraelectric/dielectric type of loops. The Mn-doped PLZT AD thick fi lms exhibit high dielectric breakdown strength (DBS) of ~ 5420 kV/cm, energy-storage density (ESD) of ~ 38.7 W/cm 3 , with high energy effi ciency of ~ 71%. Additionally, the Mn-doped PLZT AD thick fi lms demonstrate a low leakage current and excellent fatigue properties, as indicated by the obtained polarization, DBS, ESD, and energy effi ciency after 10 8 cycles.
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Yoo, Kyongjun,Jeon, Byung-Gu,Chun, Sae Hwan,Patil, Deepak Rajaram,Lim, Yong-jun,Noh, Seung-hyun,Gil, Jihyo,Cheon, Jinwoo,Kim, Kee Hoon American Chemical Society 2016 NANO LETTERS Vol.16 No.12
<P>Bulk magnetite (Fe3O4), the loadstone used in magnetic compasses, has been known to exhibit magnetoelectric (ME) properties below similar to 10 K; however, corresponding ME effects in Fe3O4 nanoparticles have been enigmatic. We investigate quantitatively the ME coupling of spherical Fe3O4 nanoparticles with uniform diameters (d) from 3 to 15 nm embedded in an insulating host, using a sensitive ME susceptometer. The intrinsic ME susceptibility (MES) of the Fe3O4 nanoparticles is measured, exhibiting a maximum value of similar to 0.6 ps/m at 5 K for d = 15 nm. We found that the MES is reduced with reduced d but remains finite until d = nm, which is close to the critical thickness for observing the Verwey transition. Moreover, with reduced diameter the critical temperature below which the MES becomes conspicuous increased systematically from 9.8 K in the bulk to 19.7 K in the nanoparticles with d = 7 nm, reflecting the core-shell effect on the ME properties. These results point to a new pathway for investigating ME effect in various nanomaterials.</P>
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