Compact AC susceptometer for fast sample characterization down to 0.1 K

Yonezawa, Suguru; Higuchi, Tohru; Sugimoto, Yu; Sow, Chanchal; Maeno, Y.

doi:10.1063/1.4929871

Cited by 25 publications

(24 citation statements)

References 16 publications

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“…High-quality samples exhibit a sharp superconducting transition with T c near 1.50 K. The AC susceptibility measurements are done using a commercial system (Quantum Design, Model PPMS) with an Adiabatic Demagnetization Refrigerator (ADR) option. The coil set and data acquisition system were designed and developed in Kyoto [38]. The dimensions of the samples measured are typically 4 mm × 3 mm × 2 mm where the c-axis direction is along the shortest dimension and the AC magnetic field from the primary coil is applied parallel to the ab-plane.…”

Section: Resultsmentioning

confidence: 99%

Improved Single-Crystal Growth of Sr2RuO4

et al. 2019

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High-quality single crystals are essentially needed for the investigation of the novel bulk properties of unconventional superconductors. The availability of such crystals grown by the floating-zone method has helped to unveil the unconventional superconductivity of the layered perovskite Sr 2 RuO 4 , which is considered as a strong candidate of a topological spin-triplet superconductor. Yet, recent progress of investigations urges further efforts to obtain ultimately high-quality crystalline samples. In this paper, we focus on the method of preparation of feed rods for the floating-zone melting and report on the improvements of the crystal growth. We present details of the improved methods used to obtain crystals with superconducting transition temperatures T c that are consistently as high as 1.4 K, as well as the properties of these crystals.Despite the key experimental results supporting spin-triplet pairing [19][20][21][22][23], such a first-order transition is difficult to explain within the context of spin-triplet superconductivity. This first-order transition becomes second order when the T c is suppressed below 1.45 K, which corresponds to an impurity level of~50 ppm [10]. Thus, pristine samples with impurity levels less than 10 ppm are required in order to deepen our knowledge of the superconducting state of Sr 2 RuO 4 .Recent innovations in the design of uniaxial-stress cells enables the T c of Sr 2 RuO 4 to be enhanced up to 3.5 K when the stress is along the crystalline [100] direction [24][25][26][27]. The origin of this enhancement of T c is attributed to the Fermi-level crossing of the van-Hove singularity in one of the three quasi-two-dimensional Fermi surfaces. It is hoped that detailed investigations of this phenomenon will lead to the clarification of the superconducting symmetry and mechanism in Sr 2 RuO 4 . The T c enhancement has actually been known for many years in the eutectic crystals of Sr 2 RuO 4 with micron-size metallic Ru platelets, which introduce strong strains in Sr 2 RuO 4 near the interfaces [28][29][30]. In order to investigate the strain-induced superconducting phase, high-quality Ru-inclusion free single crystals of Sr 2 RuO 4 with a specific in-plane crystalline direction are in demand.In this study, we examine how we can further improve the quality of crystals of Sr 2 RuO 4 grown by the floating-zone method with an infrared image furnace. The floating-zone technique has been used to produce high-quality crystals of relatively large size useful for most experimental purposes including inelastic neutron scattering. Because the technique is essentially crucible-free, it can be used to achieve the minimum possible impurity levels. The floating-zone technique has been used for the successful crystal growth of Sr 2 RuO 4 [31], as well as other ruthenates [32][33][34][35][36][37]. Previous reports mainly describe optimization of the atomic compositions of the feed rod and various parameters of the final growth process. On the other hand, there are a number of processes (from pow...

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Section: Resultsmentioning

confidence: 99%

Improved Single-Crystal Growth of Sr2RuO4

et al. 2019

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“…A cut pellet of 50.6 mg (approximately 3.3 × 3.4 × 1.0 mm 3 ) was used. Alternating-current (AC) magnetic susceptibility was measured with a lockin amplifier (Stanford Research Systems, SR830) using a miniature susceptometer [35] compatible with an adiabatic demagnetization refrigerator (ADR) of a commercial apparatus (Quantum Design, PPMS).…”

Section: Methodsmentioning

confidence: 99%

Superconductivity in the nonsymmorphic line-nodal compound CaSb2

Ikeda

Kawaguchi

Koibuchi

et al. 2020

Phys. Rev. Materials

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We found superconductivity in CaSb2 with the transition temperature of 1.7 K by means of electrical-resistivity, magnetic-susceptibility, and specific-heat measurements. This material crystallizes in a nonsymmorphic structure and is predicted to have multiple Dirac nodal lines in the bulk electronic band structure protected by symmetry even in the presence of spin-orbit coupling. We discuss a possible topological superconductivity for the quasi-2-dimensional band originating mainly from one of the antimony sites.

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“…Thus, the isomer shift is most sensitive to the number of s electrons, which has a large wavefunction weight at the nuclear position, whereas p and d electrons lead to opposite weaker shift compared to s electrons via the screening effect. DC magnetization was measured using a commercial superconducting quantum interference device (SQUID) magnetometer (Quantum Design, MPMS), while χ AC was measured using a miniature susceptometer 39 , which was installed in a commercial cryostat (Quantum Design, PPMS) with an adiabatic demagnetization refrigerator (ADR) option.…”

Section: Methodsmentioning

confidence: 99%

Evolution of Superconductivity with Sr-Deficiency in Antiperovskite Oxide Sr3−xSnO

Oudah

Hausmann

Kitao

et al. 2019

Sci Rep

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Bulk superconductivity was recently reported in the antiperovskite oxide Sr3−xSnO, with a possibility of hosting topological superconductivity. We investigated the evolution of superconducting properties such as the transition temperature Tc and the size of the diamagnetic signal, as well as normal-state electronic and crystalline properties, with varying the nominal Sr deficiency x0. Polycrystalline Sr3−xSnO was obtained up to x0 = 0:6 with a small amount of SrO impurities. The amount of impurities increases for x0 > 0.6, suggesting phase instability for high deficiency. Mössbauer spectroscopy reveals an unusual Sn4− ionic state in both stoichiometric and deficient samples. By objectively analyzing superconducting diamagnetism data obtained from a large number of samples, we conclude that the optimal x0 lies in the range 0.5 < x0 < 0.6. In all superconducting samples, two superconducting phases appear concurrently that originate from Sr3−xSnO but with varying intensities. These results clarify the Sr deficiency dependence of the normal and superconducting properties of the antiperovskite oxide Sr3−xSnO will ignite future work on this class of materials.

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Compact AC susceptometer for fast sample characterization down to 0.1 K

Cited by 25 publications

References 16 publications

Improved Single-Crystal Growth of Sr2RuO4

Improved Single-Crystal Growth of Sr2RuO4

Superconductivity in the nonsymmorphic line-nodal compound CaSb2

Evolution of Superconductivity with Sr-Deficiency in Antiperovskite Oxide Sr3−xSnO

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