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Yoshichika Onuki,Rikio Settai,Kiyohiro Sugiyama,Tetsuya Takeuchi,Fuminori Honda,Yoshinori Haga,Etsuji Yamamoto,Tatsuma D. Matsuda,Naoyuki Tateiwa,Dai Aoki,Ilya Sheikin,Hisatomo Harima 한국물리학회 2013 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.63 No.3
The f-electron system in rare-earth and actinide compounds exhibit a variety of characteristicproperties including heavy fermions and unconventional superconductivity. The Fermi surface propertiesin rare-earth and actinide compounds are clarified by the de Haas-van Alphen experimentson the basis of the results of energy band calculations. The effect of pressure on the electronicstates of CeRhIn5, CeIrSi3, and YbIr2Zn20 is studied in magnetic fields. An electronic instability,including unconventional superconductivity, occurs at 2.4 GPa in CeRhIn5 and 2.6 GPa in CeIrSi3. An abrupt non-linear increase in the magnetization, namely, a metamagnetic behavior, is found inthe heavy fermion compounds, including YbT2Zn20 (T: Co, Rh, Ir). A super-heavy fermion statewith a specific heat coefficient of 10 J/(K2·mol) is realized in YbIr2Zn20 under pressure.
Naoyuki Tateiwa,Yoshinori Haga,Tatsuma D. Matsuda,Etsuji Yamamoto,Yoshichika Onuki,Zachary Fisk 한국물리학회 2013 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.63 No.3
We have studied the high-pressure magnetic property in UGe2 where ferromagnetic superconductivityappears under high pressure. In this study, we focus on the magnetic property at pressuresabove the ferromagnetic critical pressure Pc =1.6 GPa. The temperature and magnetic field dependencesof the dc-magnetization have been measured under high pressures up to 5.1 GPa by using aceramic anvil high pressure cell. At pressures above Pc, the magnetic susceptibility χ shows a broadmaximum around Tχmax and the magnetization at 2.0 K shows an abrupt increase (metamagnetictransition) at Hc. With increasing pressure, the peak structure in χ becomes broader, and thepeak position Tχmax moves to the higher temperature region. The metamagnetic field Hc increasesrapidly with increasing pressure. At pressures above 4.1 GPa, χ shows a simple temperature dependence,and the magnetization increases linearly with increasing field. These phenomena in UGe2resemble to those in the intermetallic compounds of 3d transition metals such as Co(S1−xSex) andYCo2. We discuss the experimental results by using the phenomenological spin-fluctuation theory.
Synchrotron X-ray Diffraction Study of Lipid Lamellar Structure in Stratum Corneum
( Yasuko Obata ),( Yoshinori Onuki ),( Kozo Takayama ) 한국피부장벽학회 2013 한국피부장벽학회지 Vol.15 No.2
Lipid lamellar structure in intercellular space of stratum corneum is recognized as main physical barriers against dehydration and invasion of foreign substances. For development of effective transdermal drug delivery, it is necessary to decrease those barriers temporally and reversibly. Co-administration of components which has drug absorption enhancing effect is one of the essential methodologies to increase absorption of drugs via skin. We have determined the change in lipid lamellar structure by synchrotron X-ray diffraction. Lipids in stratum corneum are only 10% in weight and possible amount of stratum corneum utilize in experiments is very small. Thus, long exposure is necessary and obtained data might be noisy in X-ray diffraction equipment in laboratory. When the stratum corneum was pretreated by l-menthol, lipid lateral packing became liquid crystal. It was considered that disorder of lamellar structure brought about increasing in drug permeation. It means that the lipid lamellar structure is one of the key parameters to evaluate physical barrier function of the skin. Lamellar structure in lipid model prepared by typical lipids in stratum corneum was also determined using synchrotron X-ray diffraction. In case of skin disease model, lateral packing was looser than that of normal skin model. It was agreed well with known data which showed greater TEWL value in disease skin. The structure analysis of lipid lamellar structure employing synchrotron X-ray diffraction is thought to be a meaningful technique possibly applied for promoting mechanism study of transdermal absorption enhancer and evaluation of barrier function of the skin.
Magnetic Phase Diagram of UCoAl
Tatsuma D. Matsuda,Naoyuki Tateiwa,Etsuji Yamamoto,Yoshinori Haga,Yoshichika Onuki,Dai Aoki,Jacques Flouquet,Zachary Fisk 한국물리학회 2013 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.63 No.3
We report precision c-axis magnetic measurements on a high-quality single crystal of the heavyfermion metamagnet UCoAl. The metamagnetic transition at HM changes from 1st order at lowtemperature to a crossover at high temperature. HM is nearly linearly increasing with increasingtemperature up to a critical temperature T0. The critical temperature T0 is determined from boththe field and the temperature dependences of magnetization to be 11 K. The field dependence ofthe Sommerfeld coefficientis estimated from M(T) by using a Maxwell relation. (H) shows astep-like decrease at HM. This behavior is consistent with the previous reports of specific heat andresistivity measurements at low temperatures.
Pressure Evolution of the Metamagnetic Transition in UCoAl As Measured Using 59Co NMR
Hisashi Kotegawa,Hiroki Nohara,Hideki Tou,Tatsuma D. Matsuda,Etsuji Yamamoto,Yoshinori Haga,Zachary Fisk,Yoshichika Onuki,Dai Aoki,Jacques Flouquet 한국물리학회 2013 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.63 No.3
We have performed NMR measurements under pressure in UCoAl with a quantum critical endpointof the metamagnetic transition from the paramagnetic phase to the ferromagnetic (FM) phase. 59Co-NMR sensitively detects the evolution of the internal field caused by applying the externalfield. The metamagnetic field Hm increases with increasing pressure consistently with other experimentalmethods, accompanied by the suppression of the magnetization in the field-induced FMphase and the magnetization jump at Hm. The loss of the NMR signal on approaching the QCEPindicates the development of the spin fluctuations.