Katsuma Yagasaki

Experimental set-up for thermopower and resistivity measurements at 100-1300 K

In this paper we describe an experimental set-up for simultaneous measurements of thermopower and electrical resistivity at temperatures from 100 K to 1300 K. Optimal configuration of electrodes and original mechanical contacts of thermocouples, current leads and potential probes with the sample make it possible to measure a large variety of materials and result in greater flexibility with respect to the sample form and dimensions. Both bulk and thin film samples with resistances in the range from 0 Ω up to 200 kΩ (1 GΩ in case of the resistivity measurement) can be investigated. Precision and high reliability of the system have been proven during more than three years of use. The resistivity and thermopower of pure Pb, Cu and Ni, and a Cr-Si thin film composite are presented as test materials to demonstrate the possibilities and accuracy of this experimental set-up.

Reentrant superconductivity of CeRu2

Magnetization curves [MC] and temperature dependence of the AC susceptibility [TS] were measured in the superconducting phase of CeRu 2 with T c =6.55 K in zero field. For fields higher than 0.8 T in [TS], the superconducting susceptibility behaves normally up to the lowest transition temperature T cL where it decreases suddenly; the field-induced reentrant superconductivity occurs at T cL and breaks very sharply to the normal state at T cH (the highest transition temperature). In [MC], an anomaly appears when the magnetization reaches to the extrapolated magnetization of the normal state at H R (reentrant field). Magnetization drops suddenly to negative in the field-increasing process for temperatures below 3.9 K, and it only increases for temperatures above 4.0 K. Reentrant superconductivity occurs between, H R and H c2 . The reentrant phase has positive magnetization in the background.

Thermopower measurements in magnetic fields up to 17 tesla using the toggled heating method

A dc method for thermopower (TP) measurements in magnetic fields up to 17 T in the temperature range from 3 K to 300 K is introduced. A special heating technique named ‘‘seesaw heating,’’ a method similar to ac methods, was developed and resulted in good thermal stability, better accuracy and a faster procedure. Chromel–constantan thermocouples were utilized for measuring probes because of small and simple temperature dependence of magnetic field effect. Finding an empirical formula for all the calibration curves of TP of Chromel enable us to measure TP at any field and at any temperature. Finally, the experimental results on ErCo2 and LaRu2 are presented as test examples to demonstrate the possibilities and accuracy of our setup.

Magnetic properties of RMn2Ge2 single crystal compounds (R=heavy rare earth)

Abstract Magnetic characteristics in RMn 2 Ge 2 with a layer structure have been studied by measurements of magnetization, electrical resistivity and neutron diffraction. Ferrimagnetic, antiferromagnetic, weak ferromagnetic and paramagnetic behaviours are observed in the sequence of increasing temperature. The transition from ferrimagnetic to antiferromagnetic states is found to be of first order with a hysteresis of 1 deg.

Thermal and elastic properties of superconducting CeRu2

Abstract The specific heat, magnetocaloric effect and elastic modulus of CeRu 2 have been measured in magnetic fields in order to clarify the unusual superconducting state. The Fulde-Ferrell state is discussed as a possible origin of multiple superconducting phases in CeRu 2 .

Electrical properties of polycrystalline SrSi2

The electrical properties of polycrystalline SrSi2 were examined by electrical resistivity measurements at temperatures ranging from 2 to 760 K and Hall coefficient measurements at temperatures ranging from 10 to 300 K. These measurements revealed that SrSi2 is a narrow-gap semiconductor with an energy gap of 0.035 eV whose dominant carriers are holes.

Evidence of multiple superconducting phases in CeRu2

Magnetoresistance, thermopower, Hall resistivity, ac susceptibility and magnetization have been measured for CeRu 2 in the normal and superconducting phases. In the normal state, there is a magnetic anomaly at 50 K, which is presumably due to development of antiferromagnetic order. The H-T superconducting phase diagram obtained from ac susceptibility indicates the possibility of multiple superconducting phases.

Anomalous magnetotransport in (Y1-xGdx)Co2alloys: Interplay of disorder and itinerant metamagnetism

New mechanism of magnetoresistivity in itinerant metamagnets with a structural disorder is introduced basing on analysis of experimental results on magnetoresistivity, susceptibility, and magnetization of structurally disordered alloys

Transport Properties of Heusler Compounds Fe3-xVxAl

({\mathrm{Y}}_{1\ensuremath{-}x}{\mathrm{Gd}}_{x}){\mathrm{Co}}_{2}.

Strongly nonlinear electronic transport in Cr-Si composite films

In this series,