A5042035331- Magnetic properties of thin films
- Metallic Glasses and Amorphous Alloys
- Pulsars and Gravitational Waves Research
- Theoretical and Computational Physics
- Physics of Superconductivity and Magnetism
- Thin-Film Transistor Technologies
- Magnetic Properties and Applications
- Gamma-ray bursts and supernovae
- Magnetic and transport properties of perovskites and related materials
- Silicon Nanostructures and Photoluminescence
- Magnetic Properties of Alloys
- Phase-change materials and chalcogenides
- Superconducting Materials and Applications
- Advanced Condensed Matter Physics
- High-pressure geophysics and materials
- Astrophysical Phenomena and Observations
- Thermal properties of materials
- Quantum and electron transport phenomena
- Semiconductor materials and interfaces
- Surface and Thin Film Phenomena
- Cosmology and Gravitation Theories
- Topological Materials and Phenomena
- nanoparticles nucleation surface interactions
- Geophysics and Gravity Measurements
- ZnO doping and properties
University of California, Berkeley
2015-2024
University of California System
1998-2024
Lawrence Berkeley National Laboratory
2015-2024
Russian Academy of Natural Sciences
2018
MIREA - Russian Technological University
2018
Russian Academy of Sciences
2018
NS Kurnakova Institute of General and Inorganic Chemistry
2018
Joint Institute for Nuclear Research
2018
Research Institute of Molecular Electronics
2018
University of California, San Diego
2000-2016
This article reviews static and dynamic interfacial effects in magnetism, focusing on interfacially-driven magnetic phenomena associated with spin-orbit coupling intrinsic symmetry breaking at interfaces. It provides a historical background literature survey, but focuses recent progress, identifying the most exciting new scientific results pointing to promising future research directions. starts an introduction overview of how basic properties are affected by interfaces, then turns...
Liquid reconfigurable ferromagnetic materials Ferromagnetic show a permanent magnetic dipole, whereas superparamagnetic ones only properties under an applied field. Some materials, like ferrofluids, liquid-like behavior but do not retain their magnetization in the absence of Liu et al. remnant otherwise magnetite nanoparticles at oil-water interface emulsion droplets (see Perspective by Dreyfus). The could be controlled coupling and uncoupling individual nanoparticles, making it possible to...
Abstract Among topological solitons, magnetic skyrmions are two-dimensional particle-like objects with a continuous winding of the magnetization, and Hopfions three-dimensional that can be formed from closed loop twisted skyrmion strings. Theoretical models suggest stabilized in frustrated or chiral systems, target skymions transformed into by adapting their perpendicular anisotropy, but experimental verification has been elusive so far. Here, we present an study created Ir/Co/Pt multilayers...
We report on the doping dependence of order ferromagnetic metal to paramagnetic insulator phase transition in ${\mathrm{L}\mathrm{a}}_{1\ensuremath{-}x}{\mathrm{C}\mathrm{a}}_{x}{\mathrm{M}\mathrm{n}\mathrm{O}}_{3}$. At $x=0.33$, magnetization and specific heat data show a first transition, with an entropy change ($2.3\text{ }\text{ }\mathrm{J}/\mathrm{m}\mathrm{o}\mathrm{l}\text{ }\mathrm{K}$) accounted for by both volume expansion discontinuity...
A new microcalorimeter for measuring heat capacity of thin films in the range 1.5–800 K is described. Semiconductor processing techniques are used to create a device with an amorphous silicon nitride membrane as sample substrate, Pt film resistor temperatures greater than 40 K, and either Nb–Si or novel boron-doped polycrystalline thermometer lower temperatures. The addenda device, including 4×10−6 J/K at room temperature 2×10−9 4.3 approximately two orders magnitude less any existing...
Levitation of a magnet over type II superconductor where the field at exceeds Hc1 is described and shown. The penetration pinning flux lines in cause position to be stable flat disk; complete Meissner effect would make this unstable. Furthermore, observed dependence height levitation on such variables as thickness superconducting disk size are consistent with model paper based energy cost through vortices inconsistent model.
A spin reorientation accompanying the temperature-induced antiferromagnetic (AFM) to ferromagnetic (FM) phase transition is reported in strained epitaxial FeRh thin films. $^{57}\mathrm{Fe}$ conversion electron M\"ossbauer spectrometry showed that Fe moments have different orientations grown on thick single-crystalline MgO and ion-beam-assist-deposited (IBAD) MgO. It was also observed, both samples, switch at AFM FM transition. Perpendicular anisotropy evidenced of film IBAD regular...
Ultrafast control of the magnetization in ps timescales by fs laser pulses offers an attractive avenue for applications such as fast magnetic devices logic and memory. However, ultrafast helicity-independent all-optical switching (HI-AOS) has thus far only been observed Gd-based, ferrimagnetic amorphous (\textit{a}-) rare earth-transition metal (\textit{a}-RE-TM) systems, a comprehensive understanding reversal mechanism remains elusive. Here, we report HI-AOS...
Magnetization, susceptibility, and specific heat measurements were made on a single crystal of ${\mathrm{La}}_{0.75}{\mathrm{Sr}}_{0.25}{\mathrm{MnO}}_{3}.$ The ferromagnetic-to-paramagnetic phase transition was found at 346 K four critical exponents measured as: $\ensuremath{\alpha}=0.05\ifmmode\pm\else\textpm\fi{}0.07,$ $\ensuremath{\beta}=0.40\ifmmode\pm\else\textpm\fi{}0.02,$ $\ensuremath{\gamma}=1.27\ifmmode\pm\else\textpm\fi{}0.06,$...
We report the thermal conductivity and specific heat of amorphous silicon thin films measured from 5--300 K using silicon-nitride membrane-based microcalorimeters. Above 50 thin-film agrees with values previously reported by other authors. However, our data show no plateau, a low $T$ suppression that suggests scattering long wavelength, $Q$ vibrations goes as ${Q}^{2}$. The shows Debye-like behavior below 15 K, ${\ensuremath{\theta}}_{D}=487\ifmmode\pm\else\textpm\fi{}5\text{ }\text{...
The evolution of ferromagnetic (FM) domains across the temperature-driven antiferromagnetic (AF) to FM phase transition in uncapped and capped epitaxial FeRh thin films was studied by x-ray magnetic circular dichroism photoemission electron microscopy. coexistence AF phases evidenced broad different stages nucleation, growth, coalescence were directly imaged. nucleates into single domain islands width an individual nucleus is sharper than that a macroscopic average.
FeRh undergoes an unusual antiferromagnetic-to-ferromagnetic (AFM-FM) transition just above room temperature (T(AFM>FM)) that can be tuned or even completely suppressed with small changes in composition. The underlying temperature-dependent entropy difference between the competing AFM and FM states drives this is measured by specific heat as a function of from 2 to 380 K on two nearly equiatomic epitaxial Fe-Rh films, one ferromagnetic ground state (Fe-rich) other antiferromagnetic...
Stoichiometric FeRh undergoes a temperature-induced antiferromagnetic (AFM) to ferromagnetic (FM) transition at $\ensuremath{\sim}350\text{ }\text{ }\mathrm{K}$. In this Letter, changes in the electronic structure accompanying are investigated epitaxial thin films via bulk-sensitive valence-band and core-level hard x-ray photoelectron spectroscopy with photon energy of 5.95 keV. Clear differences between AFM FM states observed across entire spectrum these well reproduced using...
The ubiquitous low-energy excitations, known as two-level tunneling systems (TLSs), are one of the universal phenomena amorphous solids. Low temperature elastic measurements show that $e$-beam silicon ($a\text{\ensuremath{-}}\mathrm{Si}$) contains a variable density TLSs which diminishes growth reaches $400\text{ }\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}$. Structural analyses these $a\text{\ensuremath{-}}\mathrm{Si}$ films become denser and more structurally ordered. We conclude...
The specific heat C of e-beam evaporated amorphous silicon (a-Si) thin films prepared at various growth temperatures T(S) and thicknesses t was measured from 2 to 300 K, along with sound velocity v, shear modulus G, density n(Si), Raman spectra. Increasing results in a more ordered network increases decrease bond angle disorder. Below 20 an excess is seen less than full where it typical solid, both linear term characteristic two-level systems (TLS) additional (non-Debye) T3 contribution....
Harmonic measurements of the longitudinal and transverse voltages in Bi-Sb/Co bilayers are presented. A large second harmonic voltage signal due to ordinary Nernst effect is observed. In experiments where a magnetic field rotated film plane, shows same angular dependence as dampinglike spin-orbit torque unidirectional spin-Hall magnetoresistance, respectively. Therefore, can be spurious measurements, leading an overestimation angle conductivity topological insulators or semimetals.
Ultrafast magnetization switching at picosecond and sub-picosecond time scales has tremendous technological potential but still poses numerous questions regarding the underlying quantum mechanical phenomena, including roles of interactions between electrons, spins, phonons (lattice). At nanometer-scale dimensions relevant for modern applications, these phenomena become increasingly more pronounced. Until now, helicity-independent all-optical (HI-AOS) been largely limited to amorphous...
Direct measurements of heat capacity from 80 to 540 K antiferromagnetic superlattices NiO (high N\'eel temperature ${T}_{N}$), CoO (low and MgO (nonmagnetic) are used study the effect exchange coupling layer thickness on magnetic ordering. NiO/CoO with thin layers show a single peak similar N${\mathrm{i}}_{0.5}$C${\mathrm{o}}_{0.5}$O alloy; increasing thickness, splits into two maxima. Finite size effects seen in uncoupled CoO. Observed shifts ${T}_{N}$ importance correlation lengths spin...
(100) and (111) oriented single-crystal ${\mathrm{CoPt}}_{3}$ films were deposited over a range of growth temperatures from $\ensuremath{-}$50 to $800{}^{\ensuremath{\circ}}$C. The Curie temperature is increased by $200{}^{\ensuremath{\circ}}$C the value expected for homogeneous alloy in as-deposited (of both orientations) grown near $400{}^{\ensuremath{\circ}}$C. We interpret this as evidence previously unobserved, surface-mediated, magnetically driven miscibility gap vapor-deposited films....
We have measured the pinning force due to twin boundaries by measuring magnetic torque produced when a field is applied perpendicular c axis and rotated with respect ab axes. At 76 K, increases roughly fourfold, within 2° of parallel boundaries. This peak absent at 27 K. Irradiation 5×1016 cm−2 3.5 MeV protons overall critical current eliminates peaks observed
Coherent magnetic anisotropy is shown to be induced in vapor-deposited amorphous Tb-Fe by a thermally activated growth process. This process hypothesized involve rearrangement of local adatom configurations into energetically favorable orientations which minimize surface energy during the growth, analogous frequently observed crystallographic texturing polycrystalline thin films. The found independent state stress film and does not depend on thickness; these results are inconsistent with...
The resolution of optical microscopy can be extended beyond the diffraction limit by placing a source or detector visible light having dimensions much smaller than wavelength, λ, in near-field sample (<λ/10). This technique, scanning microscopy, is sensitive to variety important properties including density, refractive index, luminescence, and birefringence. Although image contrast based on certain characteristics similar that observed traditional strong coupling between probe often...