717 research outputs found
Local density of states and superconducting gap in the iron chalcogenide superconductor FeSeTe observed by scanning tunneling spectroscopy
We report on the first investigation of the quasiparticle local density of
states and superconducting gap in the iron chalcogenide superconductor
FeSeTe ( K). The surface of
a cleaved crystal revealed an atomic square lattice, superimposed on the
inhomogeneous background, with a lattice constant of \AA without any
reconstruction. Tunneling spectra measured at 4.2 K exhibit the superconducting
gap, which completely disappears at 18 K, with a magnitude of meV,
corresponding to .In stark contrast
to the cuprate superconductors, the value of the observed superconducting gap
is relatively homogeneous, following a sharp distribution with a small standard
deviation of 0.23 meV. Conversely, the normal-state local density of states
observed above shows spatial variation over a wide energy
range of more than 1 eV, probably due to the excess iron present in the
crystal.Comment: 4 pages, 5 figure
Novel slow dynamics of phase transition in the partially ordered frustrated magnet DyRu2Si2
DyRu2Si2 is a frustrated magnet to exhibit multiple magnetic phase transition
in zero and finite magnetic fields. We investigated and characterized the phase
transition between the partially-ordered antiferromagnetic phases at zero field
by ac susceptibility measurements. Detailed ac susceptibility measurements
reveal the novel critical dynamics of the phase transition; extremely slow
dynamics with the relaxation time in the order of 10-100 msec, speed-up of the
dynamics on cooling indicating its non-thermally activated origin and growing
of the ferromagnetic correlations towards the phase transition temperature. On
the basis of these findings, we propose the novel phase transition process,
namely, the spontaneous striped-arrangement of the precedently emergent
"belt-like" ferromagnetic spin texture.Comment: Accepted by JPSJ
URL:https://journals.jps.jp/doi/10.7566/JPSJ.92.09470
Electrostatic Micro Mirror Array with Batch-Fabricated Torsion Beam of Silicon Nanowire
2020 IEEE 33rd International Conference on Micro Electro Mechanical Systems (MEMS), 18-22 Jan. 2020.A new design of arrayed micro mirror device for a high performance spatial light modulator of high resonant frequency, large deflection angle with high mechanical reliability has been proposed. The mirror has 100-μm square plate of 5 μm thick, which is suspended by thin silicon nanowire of about 1 μm thick and wide. The device was fabricated using Bosch process and isotropic plasma etching. We successfully demonstrated array operation of 4×4 devices at relatively low actuation voltage (~20 Vpp) and large mechanical deflection amplitude (~9°). However, the deviation of vibration amplitude was large among unit resonators. By fitting the frequency response to the Duffing equation we found that self-enhancing actuation force caused by nonlinearity of the vertical combs was a main reason
Single crystal synthesis and magnetic properties of Co²⁺-substituted and non-substituted magnetoplumbite-type Na–La ferrite
Single crystals of magnetoplumbite-type Na–La ferrite with and without Co doping were grown by the flux method. Wave length dispersive X-ray analysis reveals that Na and La are present in the ratio of Na/La = 0.25–0.41, and Co is successfully substituted for Fe. Magnetization measurements using single crystals indicate uniaxial magnetic anisotropy in these materials. A metamagnetic transition for the hard-axis magnetization was observed in non Co²⁺-substituted samples at around 7 kOe due to the magnetic free energy double minima originating from the Fe²⁺ ion. The successful introduction of Co²⁺ enhances the uniaxial magnetic anisotropy favorable for permanent magnets
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