カゴ状化合物RT2Zn20 (R: 希土類, T=Ru, Rh, Os, Ir) の磁性, 超伝導およびフォノン物性

内容の要約広島大学(Hiroshima University)博士(理学)Doctor of Sciencedoctora

Ferromagnetic Transition in a Caged Compound NdOs2Zn20

AbstractMagnetic properties in a caged compound NdOs2Zn20 have been studied by the measurements of magnetization M, magnetic susceptibility M/B, and specific heat C. The measurements indicate that NdOs2Zn20 shows a structural transition at Ts = 62K and a ferromagnetic transition at TC = 0.6K. The structural transition is also observed in the La counter-part LaOs2Zn20 at Ts = 151K. The results of M (T)/B, M (B), and C(T) of NdOs2Zn20 are reproduced by a crystalline electrical field scheme with a Kramers doublet ground state

Improved accuracy in high-frequency AC transport measurements in pulsed high magnetic fields

We show theoretically and experimentally that accurate transport measurements are possible even within the short time provided by pulsed magnetic fields. For this purpose, a new method has been devised, which removes the noise component of a specific frequency from the signal by taking a linear combination of the results of numerical phase detection using multiple integer periods. We also established a method to unambiguously determine the phase rotation angle in AC transport measurements using a frequency range of tens of kilohertz. We revealed that the dominant noise in low-frequency transport measurements in pulsed magnetic fields is the electromagnetic induction caused by mechanical vibrations of wire loops in inhomogeneous magnetic fields. These results strongly suggest that accurate transport measurements in short-pulsed magnets are possible when mechanical vibrations are well suppressed

Magnetic and transport properties of single crystalline RCoxSn2 (R = Ce and La)

In this study, single crystals of CeCo0.39Sn2 and LaCo0.43Sn2 were grown by the Czochralski pulling method for the first time. These compounds crystallize to the orthorhombic CeNiSi2 type structure with the space group Cmcm. The inverse magnetic susceptibility χ−1 of CeCo0.39Sn2 obeys a Curie-Weiss law above 100 K. The effective magnetic moment is close to the value expected for the Ce3+ ion, indicating that the Ce 4f electrons in CeCo0.39Sn2 are well localized. No magnetic transition is observed down to 2 K. However, the specific heat exhibits an upturn upon cooling below 8 K, suggesting that a magnetic order would occur below 2 K