arXiv subjects

H. Mizuno

Publications and source records attributed to H. Mizuno.

4 recordsLinked to original sources

arXiv2019

Impact of elastic heterogeneity on the propagation of vibrations at finite temperatures in glasses

Some aspects of how sound waves travel through disordered solids are still unclear. Recent work has characterized a feature of disordered solids which seems to influence vibrational excitations at the mesoscales, local elastic heterogeneity. Sound waves propagation has been demonstrated to be strongly affected by inhomogeneous mechanical features of the materials which add to the standard anharmonic couplings, amounting to extremely complex transport properties at finite temperatures. Here, we address these issues for the case of a simple atomic glass former, by Molecular Dynamics computer simulation. In particular, we focus on the transverse components of the vibrational excitations in terms of dynamic structure factors, and characterize the temperature dependence of sound dispersion and attenuation in an extended frequency range. We provide a complete picture of how elastic heterogeneity determines transport of vibrational excitations, also based on a direct comparison of the numerical data with the predictions of the heterogeneous elastic theory.

cond-mat.soft↗

arXiv2015

Extraction of the Anomalous Nernst Effect in the Electric Measurement of the Spin Orbit Torque

Spin orbit torque has been intensively investigated because of its high energy efficiency in manipulating a magnetization. Although various methods for measuring the spin orbit torque have been developed so far, the measurement results often show inconsistency among the methods, implying that an electromotive force, such as Nernst effect, irrelevant to the spin orbit torque may affect the measurement results as an artifact. In this letter, we developed a unique method to distinguish the spin orbit torque and the anomalous Nernst effect. The measurement results show that the spin orbit torque can be underestimated up to 50% under the influence of the anomalous Nernst effect.

cond-mat.mtrl-sci↗

arXiv2003

Ac Susceptibility and Static Magnetization Measurements of CeRu$_2$Si$_2$ at Small Magnetic Fields and Ultra Low Temperatures

The magnetic properties of CeRu$_2$Si$_2$ at microkelvin temperatures (down to 170 $μ$K) and ultra small magnetic fields ($0.02\sim6.21$ mT) are investigated experimentally for the first time. The simultaneously measured ac susceptibility and static magnetization show neither evidence of the magnetic ordering, superconductivity down to the lowest temperatures nor conventional Landau Fermi-Liquid behavior. The results imply the magnetic transition temperature in undoped CeRu$_2$Si$_2$ is very close to absolute 0 K. The possibility for proximity of CeRu$_2$Si$_2$ to the quantum critical point without any doping is discussed.

cond-mat.str-el↗

arXiv2000

High Power Testing Results of the X-Band Mixed-Mode RF Windows for Linear Colliders

In this paper, we summarize the high power testing results of the X-band mixed-mode RF windows at KEK and SLAC for linear colliders. The main feature of these windows is that the combination of modes on the surface of the ceramic significantly decreases the electric and magnetic fields in the junction between the ceramic and the metal. So far two types of high power windows (with the diameter of 53 mm and 64 mm) have been fabricated. A high power model of the smaller type window was fabricated and tested in a resonant ring at KEK. A maximum circulating power of 81 MW with 300 ns duration or 66 MW with 700 ns duration was achieved. Light emission was observed for a power level of over 10 MW. Later, both windows were shipped to SLAC for even higher power testing using combined power from two klystrons. The first window (53 mm diameter) achieved a transmitted power of 80 MW with 1.5 microsec duration at 30 Hz repetition. It was not destroyed during the testing. The testing of the second window was carried out next to the small type and achieved 62 MW with 1.5 maicrosec duration with 10 Hz repetition. The final results of both windows are presented in this report.

hep-ex↗