Spin-dependent electron attenuation by transmission through thin ferromagnetic films

Pappas, David P.; Kämper, K. P.; Miller, B. P.; Hopster, H.; Fowler, David E.; Brundle, C. R.; Luntz, A. C.; Shen, Zhi‐Xun

doi:10.1103/physrevlett.66.504

Cited by 188 publications

(62 citation statements)

References 14 publications

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“…This is the principle of some polarizers, for example for the helicity of X-rays [51] or spin of electrons [52]. Aside from obvious issues arising from the signal-over-noise ratio, we found out that in practice an instrumental effect limits the contrast.…”

Section: Background Level In Peem Imagingmentioning

confidence: 86%

Quantitative analysis of shadow x-ray magnetic circular dichroism photoemission electron microscopy

et al. 2015

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Shadow X-ray Magnetic Circular Dichroism Photo-Emission Electron Microscopy (XMCD-PEEM) is a recent technique, in which the photon intensity in the shadow of an object lying on a surface, may be used to gather information about the three-dimensional magnetization texture inside the object. Our purpose here is to lay the basis of a quantitative analysis of this technique. We first discuss the principle and implementation of a method to simulate the contrast expected from an arbitrary micromagnetic state. Text book examples and successful comparison with experiments are then given. Instrumental settings are finally discussed, having an impact on the contrast and spatial resolution : photon energy, microscope extraction voltage and plane of focus, microscope background level, electric-field related distortion of three-dimensional objects, Fresnel diffraction or photon scattering.Progress is continuous in the decreasing size and increasing complexity of nanosized magnetic systems being designed for either fundamental science or devices. Magnetic microscopies are crucial tools to monitor and understand the properties of such systems. Various types of information are desirable to gather, leading to multiple criteria to classify microscopies: spatial and time resolution, compatibility with environmental parameters such as variable temperature and applied magnetic field, requirements on the sample preparation and compatibility for ex-situ processing such as lithography, correlation with structural information, elemental sensitivity, quantity measured (magnetization, induction, stray field etc.), sensitivity. The most common magnetic microscopies offering spatial resolution below 50 nm and direct sensitivity to magnetization are X-ray Magnetic Circular Dichroism PhotoEmission Electron Microscopy (XMCD-PEEM) [ [7][8][9].Yet another criterion is the volume of the sample probed. This criterium is gaining in importance in the context of the emergence of three-dimensional (3D) magnetic objects and textures. The distribution of magnetization may be truly 3D if along the three directions in space the size of a system lies above magnetic characteristic length scales, such as the dipolar exchange length ∆ d for soft magnetic materials, or the anisotropy exchange length ∆ u for a hard magnetic material [10]. While this is obviously fulfilled in macroscopic materials, the complexity of magnetic textures is such that it cannot be measured in detail, and besides it cannot be controlled to achieve specific functions. The progress in nanofabrication techniques now allows to design suitable systems, both with top-down and bottom-up approaches. Let us give some examples. Flat magnetic elements are basic building blocks in spintronics, being patterned with great 2D versatility with thin film and lithography technologies. Large lateral dimensions may give rise to 2D magnetic textures, such as the so-called vortex state in disks [11]. Such textures are being investigated to design RF oscillator components, relying on the gyrotropic motion ...

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Section: Background Level In Peem Imagingmentioning

confidence: 86%

Quantitative analysis of shadow x-ray magnetic circular dichroism photoemission electron microscopy

et al. 2015

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“…Similar to the physics of GMR structures (Gijs and Bauer, 1997;Levy and Mertig, 2002), scattering in the base region strongly depends on the relative orientation of the magnetizations in the ferromagnetic layers. Electrons with spin which has magnetic moment opposite (antiparallel) to the magnetization of a ferromagnetic layer typically are scattered more than electrons with parallel magnetic moment, resulting in a spin-filtering effect which can be described in terms of a spin-dependent mean free path (Rendell and Penn, 1980;Pappas et al, 1991;Hong and Mills, 2000). Generally, both elastic and inelastic scattering processes determine the effective spin-dependent mean free path, 120 These efforts are motivated in part by the success of (spininsensitive) ballistic electron-emission microscopy in providing high spatial and energy resolution of the properties of metal/ semiconductor interfaces (Kaiser and Bell, 1988;Smith et al, 2000;Bonnell, 2001).…”

Section: Hot-electron Spin Transistorsmentioning

confidence: 99%

Spintronics: Fundamentals and applications

2004

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Spintronics, or spin electronics, involves the study of active control and manipulation of spin degrees of freedom in solid-state systems. This article reviews the current status of this subject, including both recent advances and well-established results. The primary focus is on the basic physical principles underlying the generation of carrier spin polarization, spin dynamics, and spin-polarized transport in semiconductors and metals. Spin transport differs from charge transport in that spin is a nonconserved quantity in solids due to spin-orbit and hyperfine coupling. The authors discuss in detail spin decoherence mechanisms in metals and semiconductors. Various theories of spin injection and spin-polarized transport are applied to hybrid structures relevant to spin-based devices and fundamental studies of materials properties. Experimental work is reviewed with the emphasis on projected applications, in which external electric and magnetic fields and illumination by light will be used to control spin and charge dynamics to create new functionalities not feasible or ineffective with conventional electronics. CONTENTS

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“…With some notable exceptions [52,[125][126][127][128][129], the information reported by the lowenergy photoelectrons imaged in PEEM primarily originates from within a nanometer of the sample surface [53]. In this zone, optical interactions dominate the electron environment.…”

Section: Photonics 6 Photoemission and Photonicsmentioning

confidence: 99%

Aberration Corrected Photoemission Electron Microscopy with Photonics Applications

Fitzgerald¹

2000

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Photoemission electron microscopy (PEEM) uses photoelectrons excited from material surfaces by incident photons to probe the interaction of light with surfaces with nanometer-scale resolution. The point resolution of PEEM images is strongly limited by spherical and chromatic aberration. Image aberrations primarily originate from the acceleration of photoelectrons and imaging with the objective lens and vary strongly in magnitude with specimen emission characteristics. Spherical and chromatic aberration can be corrected with an electrostatic mirror, and here I develop a triode mirror with hyperbolic geometry that has two adjacent, field-adjustable regions. I present analytic and numerical models of the mirror and show that the optical properties agree to within a few percent. When this mirror is coupled with an electron lens, it can provide a large dynamic range of correction and the coefficients of spherical and chromatic aberration can be varied independently. I report on efforts to realize a triode mirror corrector, including design, characterization, and alignment in our microscope at Portland State University (PSU). PEEM may be used to investigate optically active nanostructures, and we show that photoelectron emission yields can be identified with diffraction, surface plasmons, and dielectric waveguiding.Furthermore, we find that photoelectron micrographs of nanostructured metal and dielectric structures correlate with electromagnetic field calculations. We conclude that photoemission is highly spatially sensitive to the electromagnetic field intensity, allowing the direct visualization of the interaction of light with material surfaces at nanometer scales and over a wide range of incident light frequencies.ii

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Spin-dependent electron attenuation by transmission through thin ferromagnetic films

Cited by 188 publications

References 14 publications

Quantitative analysis of shadow x-ray magnetic circular dichroism photoemission electron microscopy

Quantitative analysis of shadow x-ray magnetic circular dichroism photoemission electron microscopy

Spintronics: Fundamentals and applications

Aberration Corrected Photoemission Electron Microscopy with Photonics Applications

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