Tunneling magnetoresistance was found to be suppressed with decreasing temperature for magnetic tunnel junctions (MTJs) oxidized under high plasma power. A strong temperature dependence of the junction resistance was observed, along with zero-bias anomalies of dynamic resistance at low temperatures. Resistance shows a logarithmic dependence on temperature, and resistance versus temperature exhibits a scaling behavior. Our experimental data can be explained in a consistent way by the Kondo effect in the MTJs with the Kondo temperature TK=20-30 K.
Based on the detailed Mn L(2,3)-edge x-ray resonant scattering results, we report a new complexity in the magnetic order of multiferroic orthomangnites, which has been considered as the simple A-type cycloid order inducing ferroelectricity. The Dzyaloshinskii-Moriya interaction involved in the orthorhombic distortion brings on F-type canting from the A type, and the ordering type becomes the off-phase synchronized bc cycloid in TbMnO(3) or the tilted antiphase ab cycloid in Eu(3/4)Y(1/4)MnO(3). The F-type canting is responsible for the magnetic field-driven multiferroicity to weak ferromagnetism transition.
We present quantitative evidence for X-ray-induced water vaporization: water is vaporized at a rate of 5.5 pL/s with the 1-Å-wavelength X-ray irradiation of ~0.1 photons per Å 2 ; moreover, water vapor is reversibly condensed during pauses in irradiation. This result fundamentally suggests that photoionization induces vaporization. This phenomenon is attributed to surface tension reduction by ionization and would be universally important in radiological and electrohydrodynamic situations.PACS numbers: 68.03. Fg, 68.03.Cd, 78.70.-g * E-mail: bmweon@hotmail.com, † jhje@postech.ac.krBrief Report -Physical Review E -2 -X-ray photonics is undergoing a revolution in imaging capabilities with the use of ultrabright X-ray sources. X-ray imaging at the nano-and microscale is of great interest for applications in physical and life sciences, including X-ray physics, materials science, biological imaging, environmental analysis, archaeology, paleontology, and heritage restoration [1], because it facilitates the nondestructive, direct visualization of internal structures or elements.Meanwhile, radiation damage from the energy deposited into the sample by the X-ray photons used for imaging is inevitable [2,3]. In particular, radiation-induced ionization ultimately disintegrates the sample by charge accumulation beyond a limit and is otherwise known as Coulomb explosion [2,3] and fission [4,5]. The conventional damage barrier for Coulomb explosion is known to be about 200 photons per Å 2 for X-rays with a wavelength of 1 Å [2,3].Radiation damage can be mitigated by cryofixation or by ultrabright, ultrashort X-ray pulses [2].However, radiation damage to living tissues by radiation ionization is not yet fully understood[6], although it is a limiting factor in achieving high-resolution data [2].In previous works, we demonstrated that high-brilliance X-ray photons affect the surface tension of water by inducing ionization, using hard X-ray imaging at the 7B2 beamline (dose rate ~1 kGy s -1 ) of the Pohang Light Source [7][8][9]. A charge density over ~10 -4 charges per Å 2 was required for a significant reduction (> 30%) in the surface tension [9]. This condition corresponds to X-ray irradiation of ~0.1 photons per Å 2 , following a simulation using the ionization rate of ~1 charge per Å 2 by 2000 photons per Å 2 with X-rays of 1 Å wavelength [2].We put forward a possibility of water vaporization by surface tension reduction [7,8] based on a monotonic relationship of the surface tension to the vaporization enthalpy [10,11], but quantitative evidence was lacking.To corroborate the possibility, we conducted an elaborate experiment in a different synchrotron source while applying high-speed X-ray imaging [12,13]. Using a hydrophilic capillary tube containing a small amount of water, we first made a confined water lens with concave menisci, where the left region was closed and the right one was open in air [ Fig. 1]. The changes of the water menisci were simultaneously imaged using a high-speed camera, synchronized and gated t...
A fast microtomography system for high-resolution high-speed imaging has been developed using bright monochromatic x-rays at the BL29XU beamline of SPring-8. The shortest scan time for microtomography we attained was 0.25 s in 1.25 μm effective pixel size by combining the bright monochromatic x-rays, a fast rotating sample stage, and a high performance x-ray imaging detector. The feasibility of the tomography system was successfully demonstrated by visualization of rising bubbles in a viscous liquid, an interesting issue in multiphase flow physics. This system also provides a high spatial (a measurable feature size of 300 nm) or a very high temporal (9.8 μs) resolution in radiographs.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.