Generation of flat-top pulsed magnetic fields with feedback control approach

Kohama, Yoshimitsu; Kindo, Koichi

doi:10.1063/1.4931689

Cited by 41 publications

(16 citation statements)

References 15 publications

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“…Measurements of the absolute values of the specific heat are extremely challenging in pulsed magnetic fields. These were performed in a longpulsed magnet at the International Megagauss Science Laboratory of ISSP in Kashiwa up to 43.5 T. To minimize the influence associated with the field instability of the pulsed field, we generated highly stabilized (±100 Oe) magnetic fields with a 100 ms timescale using a fieldfeedback controller 22 and measured the absolute value of the specific heat in the stabilized field by applying the heat-pulse method 23 . The resolution of the specific heat data were successfully improved 24 , and a detailed analysis of the data is possible up to 43.5 T. The optical fibre Bragg grating (FBG) method 25,26 was used to measure the magnetostriction in pulsed magnetic fields up to 60 T with B a and B c. Measurements of the dHvA effect of CeRhIn 5 were conducted utilizing a torque technique between 5 K and 300 mK in dc fields up to 45 T 8 .…”

Section: Methodsmentioning

confidence: 99%

Enhancement of the effective mass at high magnetic fields in CeRhIn5

et al. 2019

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The Kondo-lattice compound CeRhIn5 displays a field-induced Fermi surface reconstruction at B * ≈ 30 T, which occurs within the antiferromagnetic state, prior to the quantum critical point at Bc0 ≈ 50 T. Here, in order to investigate the nature of the Fermi surface change, we measured the magnetostriction, specific heat, and magnetic torque of CeRhIn5 across a wide range of magnetic fields. Our observations uncover the field-induced itineracy of the 4f electrons, where above Bonset ≈ 17 T there is a significant enhancement of the Sommerfeld coefficient, and spin-dependent effective cyclotron masses determined from quantum oscillations. Upon crossing Bonset, the temperature dependence of the specific heat also shows distinctly different behavior from that at low fields. Our results indicate that the Kondo coupling is remarkably robust upon increasing the magnetic field. This is ascribed to the delocalization of the 4f electrons at the Fermi surface reconstruction at B * . 1 G. R. Stewart, Non-Fermi-liquid behavior in d-and felectron metals. Rev. Mod. Phys. 73, 797 (2001).

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Section: Methodsmentioning

confidence: 99%

Enhancement of the effective mass at high magnetic fields in CeRhIn5

et al. 2019

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“…The range of standard I-V curves could also be extended by using magnetic field pulses with a flat-top (loẇ H at peak field), which, for instance, can be achieved by using feedback controllers in a compact magnet or with the 60 T long-pulse at the NHMFL. [28,39] Even if only the linear region of the I-V curves is available, these I-V curves can be fitted using Eq. 1 with J c and n as free parameters.…”

Section: Discussionmentioning

confidence: 99%

Dynamics and Critical Currents in Fast Superconducting Vortices at High pulsed Magnetic Fields

et al. 2019

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Non-linear electrical transport studies at high-pulsed magnetic fields, above the range accessible by DC magnets, are of direct fundamental relevance to the physics of superconductors, domain-wall, charge-density waves, and topological semi-metal. All-superconducting very-high field magnets also make it technologically relevant to study vortex matter in this regime. However, pulsed magnetic fields reaching 100 T in milliseconds impose technical and fundamental challenges that have prevented the realization of these studies. Here, we present a technique for sub-microsecond, smart, current-voltage measurements, which enables determining the superconducting critical current in pulsed magnetic fields, beyond the reach of any DC magnet. We demonstrate the excellent agreement of this technique with low DC field measurements on Y 0.77 Gd 0.23 Ba 2 Cu 3 O 7 coated conductors with and without BaHfO 3 nanoparticles. Exploring the uncharted high magnetic field region, we discover a characteristic influence of the magnetic field rate of change (dH/dt) on the current-voltage curves in a superconductor. We fully capture this unexplored vortex physics through a theoretical model based on the asymmetry of the vortex velocity profile produced by the applied current. arXiv:1903.04658v2 [cond-mat.supr-con]

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“…The specific heat was measured with a heat-pulse technique inside a motor-generator-driven long-pulse magnet at the International MegaGauss Science Laboratory of the University of Tokyo. 81 The experimental data points were collected during the flat-topped portion of the magnetic-field profiles created by feedback loop control, 81,82 at fields up to 37.8 T and temperatures down to 1 K.…”

Section: Methodsmentioning

confidence: 99%

Revealing three-dimensional quantum criticality by Sr substitution in Han purple

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et al. 2021

Phys. Rev. Research

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Classical and quantum phase transitions (QPTs), with their accompanying concepts of criticality and universality, are a cornerstone of statistical thermodynamics. An exemplary controlled QPT is the field-induced magnetic ordering of a gapped quantum magnet. Although numerous "quasi-one-dimensional" coupled spin-chain and -ladder materials are known whose ordering transition is three-dimensional (3D), quasi-2D systems are special for several physical reasons. Motivated by the ancient pigment Han Purple (BaCuSi2O6), a quasi-2D material displaying anomalous critical properties, we present a complete analysis of Ba0.9Sr0.1CuSi2O6. We measure the zero-field magnetic excitations by neutron spectroscopy and deduce the magnetic Hamiltonian. We probe the field-induced transition by combining magnetization, specific-heat, torque and magnetocalorimetric measurements with low-temperature nuclear magnetic resonance studies near the QPT. By a Bayesian statistical analysis and large-scale Quantum Monte Carlo simulations, we demonstrate unambiguously that observable 3D quantum critical scaling is restored by the structural simplification arising from light Srsubstitution in Han Purple.

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Generation of flat-top pulsed magnetic fields with feedback control approach

Cited by 41 publications

References 15 publications

Enhancement of the effective mass at high magnetic fields in CeRhIn5

Enhancement of the effective mass at high magnetic fields in CeRhIn5

Dynamics and Critical Currents in Fast Superconducting Vortices at High pulsed Magnetic Fields

Revealing three-dimensional quantum criticality by Sr substitution in Han purple

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