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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.
Single Crystal Growth and Physical Properties of UT2Al20 (T=Transition Metal)
Yuji Matsumoto,Tatsuma D. Matsuda,Naoyuki Tateiwa,Etsuji Yamamoto,Yoshinori Haga,Zachary Fisk 한국물리학회 2013 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.63 No.3
We have studied the single crystal growth and the physical properties of the UT2Al20 system. Wehave successfully grown UT2Al20 (T = Cr, Ti, W and Mo) using Al self flux and have characterizedthe crystals using electron probe microanalyzer (EPAM) and X-ray diffractometer. We have alsomeasured their magnetic and electric properties. The ground states of UT2Al20 (T = Cr, Mo andW ) are Pauli paramagnetic as is likely also in UTi2Al20. The effective masses of UCr2Al20 andUTi2Al20 are only weakly enhanced.
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.
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.
Anomalous Hall Effect in Rare Earth Antiferromagnets with the Hexagonal Structures
Yoshichika ?nuki,Kenri Nakaima,Wataru Iha,Shinya Matsuda,Masato Hedo,Takao Nakama,Dai Aoki,Ai Nakamura,Miho Nakashima,Yasushi Amako,Tetsuya Takeuchi,Tatsuma D. Matsuda 한국물리학회 2023 새물리 Vol.73 No.12
We measured Hall resistivities in nine antiferromagnets with the AlB<SUB>2-</SUB> and ZrNiAl-types hexagonal structures and found characteristic magnetic phases especially in ErGa₂ and HoAgGe.
Naoto Metoki,Hironori Sakai,Yasunori Haga,Tatsuma D. Matsuda,Shugo Ikeda 한국물리학회 2013 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.62 No.12
The magnetic excitation of a narrow gap semiconductor β-US2 was studied by means of neutronscattering. At low temperatures, clear crystalline electric-field (CEF) excitations were observed,indicating the localized character of 5f electrons. The pseudo-doublet state at an excitation energyof 7 meV is consistent with the level scheme based on the 5f2 configuration of U4+ ions, whichreproduces the magnetic susceptibility, magnetization, and specific heat. At elevated temperatures,the conductivity recovers, with the excitation of 5f carriers being beyond the conduction gap of 90K. Simultaneously, the CEF excitation becomes weak and broad, and is replaced by a quasi-elasticresponse of magnetic origin, indicating a crossover of the 5f character from localized to itinerant.
29Si-NMR Study of Antiferromagnet CeRh2Si2 Using Single Crystals
Hironori Sakai,Yo Tokunaga,Shinsaku Kambe,Yuji Matsumoto,Tatsuma D. Matsuda,Yoshinori Haga 한국물리학회 2013 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.63 No.3
29Si-NMR Study of antiferromagnet CeRh2Si2 with a tetragonal ThCr2Si2-type structure hasbeen performed using single crystals. The Knight shifts along the a and the c axes have beenmeasured as a function of temperatures in the paramagnetic state. At ambient pressure, the Knightshifts show the Ising-type anisotropy along the c axis, which is similar to the magnetic susceptibility. The hyperfine coupling constants for 29Si along the a and the c axes have been determined fromKnight shift versus static susceptibility plots.
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.