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Synthesis and characterization of the heavy-fermion compound CePtAl<sub>4</sub>Ge<sub>2</sub>
Shin, Soohyeon,Rosa, Priscila F.S.,Ronning, Filip,Thompson, Joe D.,Scott, Brian L.,Lee, Sangyun,Jang, Harim,Jung, Soon-Gil,Yun, Eunbhin,Lee, Hyoyoung,Bauer, Eric D.,Park, Tuson Elsevier 2018 JOURNAL OF ALLOYS AND COMPOUNDS Vol.738 No.-
<P><B>Abstract</B></P> <P>We report the synthesis of the Ce-based quaternary compound CePtAl<SUB>4</SUB>Ge<SUB>2</SUB> that crystallizes in the trigonal structure (space group <I>R</I> 3 ¯ <I>m</I>, 166) with unit cell parameters, <I>a</I> = 4.1995(5) Å, <I>c</I> = 31.851(7) Å, and γ = 120°. Powder X-ray diffraction and energy dispersive X-ray spectroscopy show that CePtAl<SUB>4</SUB>Ge<SUB>2</SUB> (LaPtAl<SUB>4</SUB>Ge<SUB>2</SUB>) is in a single, homogeneous phase. Magnetic susceptibility, electrical resistivity, and heat capacity measurements of CePtAl<SUB>4</SUB>Ge<SUB>2</SUB> show that it exhibits antiferromagnetic behavior below 2.3 K. The magnetic susceptibility for the magnetic field applied perpendicular (χ<SUB>ab</SUB>) and parallel (χ<SUB>c</SUB>) to the crystalline c-axis is very anisotropic, and the susceptibility ratio (χ<SUB>ab</SUB>/χ<SUB>c</SUB>) reaches a maximum value of 10, indicating that the spin easy axis is within the Ce plane. The entropy recovered at <I>T</I> <SUB>N</SUB> is consistent with the doublet ground state of the crystal field split <I>J</I> = 5/2 multiplet of Ce<SUP>3+</SUP> ions.</P> <P><B>Highlights</B></P> <P> <UL> <LI> CePtAl<SUB>4</SUB>Ge<SUB>2</SUB> synthesized by the Al/Ge flux method adopts the trigonal structure. </LI> <LI> CePtAl<SUB>4</SUB>Ge<SUB>2</SUB> is an antiferromagnet with <I>T</I> <SUB>N</SUB> of 2.3 K. </LI> <LI> CePtAl<SUB>4</SUB>Ge<SUB>2</SUB> is a heavy fermion compound with the effective mass of 205 mJ mol<SUP>−1</SUP> K<SUP>−2</SUP>. </LI> <LI> The entropy at <I>T</I> <SUB>N</SUB> is consistent with the doublet ground state of J = 5/2 of Ce<SUP>3+</SUP> ions. </LI> </UL> </P>
Jaewon Shin,Harim Lee,Seunghyun Ahn,Won Seok Jeong,CheongTaek Kim,Seyeon Park 한국응용생명화학회 2022 Journal of Applied Biological Chemistry (J. Appl. Vol.65 No.4
In this study, derivatives of trimethoxybenzene were investigated as inhibitors of melanogenesis. We examined the effects of methyl 3,4,5-trimethoxybenzoate (MTB), ethyl 3,4,5- trimethoxybenzoate (ETB), methyl 3,4,5-trimethoxycinnamate (MTC), and ethyl 3,4,5-trimethoxycinnamate (ETC). First, the inhibitory effects of these agents on melanin production were evaluated using α-melanocyte-stimulating hormone (α-MSH)- stimulated B16F10 melanoma cells. We found that all derivatives decreased α-MSH-induced melanin production in B16F10 melanoma cells; ETC showed a strong inhibitory effect at half of the concentration of the other derivatives. As tyrosinase is considered a key enzyme of melanogenesis, we also examined whether the derivatives inhibited tyrosinase activity. MTC and ETC reduced mushroom tyrosinase activity and expression levels of α-MSH-induced B16F10 cellular tyrosinase protein. Inhibitory effects of all derivatives on α-MSH-induced B16F10 cellular tyrosinase activity were shown in a dose-dependent manner. Additionally, the derivatives were exposed to diphenylpicrylhydrazyl free radical to examine their antioxidant characteristics. All derivatives showed considerable antioxidant activity, which was 2-fold higher than that of arbutin. In conclusion, the trimethoxybenzene derivatives, including MTB, ETB, MTC, and ETC exerted anti-melanogenic and antioxidant effects on α-MSHstimulated melanogenesis, demonstrating their potential for use as novel hypopigmenting agents and antioxidants.
Jung, Soon-Gil,Shin, Soohyeon,Jang, Harim,Mikheenko, Pavlo,Johansen, Tom H,Park, Tuson IOP Publishing Ltd 2017 Superconductor science & technology Vol.30 No.8
<P>We investigate the effects of magnetic impurities on the upper critical field (<I>μ</I> <SUB>0</SUB> <I>H</I> <SUB>c2</SUB>) in La-doped CaFe<SUB>2</SUB>As<SUB>2</SUB> (LaCa122) single crystals. The magnetic field dependency of the superconducting transition temperature (<I>T</I> <SUB>c</SUB>) for LaCa122 is rapidly suppressed at low fields up to ∼1 kOe despite its large <I>μ</I> <SUB>0</SUB> <I>H</I> <SUB>c2</SUB>(0) value on the order of tens of Tesla, resulting in a large positive curvature of <I>μ</I> <SUB>0</SUB> <I>H</I> <SUB>c2</SUB>(<I>T</I>) near <I>T</I> <SUB>c</SUB>. The magnetization hysteresis (<I>M</I>–<I>H</I>) loop at temperatures above <I>T</I> <SUB>c</SUB> shows a ferromagnetic-like signal and the <I>M</I>(<I>H</I>) value rapidly increases with increasing magnetic field up to ∼1 kOe. Taken together with the linear suppression of <I>T</I> <SUB>c</SUB> with the magnetization in the normal state, these results suggest that the large upward curvature of <I>μ</I> <SUB>0</SUB> <I>H</I> <SUB>c2</SUB>(<I>T</I>) near <I>T</I> <SUB>c</SUB> in La-doped CaFe<SUB>2</SUB>As<SUB>2</SUB> mainly originates from the suppression of superconductivity due to the presence of magnetic impurities.</P>