Scanning electron microscopy with polarization analysis (SEMPA)

Scheinfein, M. R.; Unguris, John; Kelley, Michael H.; Pierce, Daniel T.; Celotta, Robert

doi:10.1063/1.1141908

Cited by 256 publications

(110 citation statements)

References 89 publications

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“…We image the magnetic structure of the CoFe layer at zero magnetic field using scanning electron microscopy with polarization analysis (SEMPA) 38 . By measuring the spin polarization of secondary electrons, SEMPA directly measures the local vector magnetization in the CoFe layer 39 . An example of an IP magnetization image is shown in Fig.…”

Section: Resultsmentioning

confidence: 99%

Probing electric field control of magnetism using ferromagnetic resonance

et al. 2015

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Exchange coupled CoFe/BiFeO 3 thin-film heterostructures show great promise for power-efficient electric field-induced 180°magnetization switching. However, the coupling mechanism and precise qualification of the exchange coupling in CoFe/BiFeO 3 heterostructures have been elusive. Here we show direct evidence for electric field control of the magnetic state in exchange coupled CoFe/BiFeO 3 through electric field-dependent ferromagnetic resonance spectroscopy and nanoscale spatially resolved magnetic imaging. Scanning electron microscopy with polarization analysis images reveal the coupling of the magnetization in the CoFe layer to the canted moment in the BiFeO 3 layer. Electric fielddependent ferromagnetic resonance measurements quantify the exchange coupling strength and reveal that the CoFe magnetization is directly and reversibly modulated by the applied electric field through a B180°switching of the canted moment in BiFeO 3 . This constitutes an important step towards robust repeatable and non-volatile voltage-induced 180°m agnetization switching in thin-film multiferroic heterostructures and tunable RF/microwave devices.

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Section: Resultsmentioning

confidence: 99%

Probing electric field control of magnetism using ferromagnetic resonance

et al. 2015

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“…This technique allows direct, quantitative imaging of the surface magnetization with an in-plane resolution of at least 20 nm 22 by analyzing the spin of secondary electrons from a magnetic material. The efficiency of SEMPA's low energy diffuse electron scattering spin analyzers requires a slow scan rate to analyze the magnetic state, thus allowing imaging of only the remanent magnetization state.…”

Section: Methodsmentioning

confidence: 99%

“…IV before concluding remarks are made in Sec. V. Scanning electron microscopy with polarization analysis (SEMPA) 22 was used to directly image and characterize the magnetic configuration of the domain walls and triangles in the experiments.…”

Section: Introductionmentioning

confidence: 99%

Field-driven sense elements for chirality-dependent domain wall detection and storage

Bowden

Unguris

2013

Journal of Applied Physics

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A method for locally sensing and storing data of transverse domain wall chirality in planar nanowire logic and memory systems is presented. Patterned elements, in close proximity to the nanowires, respond to the asymmetry in the stray field from the domain wall to produce a chirality-dependent response. When a bias field is applied, a stray field-assisted reversal of the element magnetization results in a reversed remanent state, measurable by scanning electron microscopy with polarization analysis (SEMPA). The elements are designed as triangles with tips pointing toward the nanowire, allowing the shape anisotropy to be dominated by the base but having a portion with lower volume and lower energy barrier closest to the domain wall. Micromagnetic modeling assists in the design of the nanowire-triangle systems and experiments using SEMPA confirm the importance of aspect ratio and spacing given a constant bias field magnitude.

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“…This effect has been taken advantage of in making polarized secondary electron scanning microscopes (or scanning electron microscope with polarization analysis, SEMPA) for high resolution magnetic domain microscopy. 88 Despite the various possibilities for loss of spin-information in transport and transmission through the surface, it has been experimentally found in many cases that spin polarization of primary photoelectrons is not significantly altered in the emission process, allowing straightforward interpretation of the experiment. In other cases things can be less clear, although even in these cases, the loss of spin-polarization can be used for understanding the energy and spin dependent scattering of excited electrons.…”

Section: Steps Two and Threementioning

confidence: 99%

A New Spin on Photoemission Spectroscopy

Jozwiak

2008

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Professor Alessandra Lanzara, ChairThe electronic spin degree of freedom is of general fundamental importance to all matter.Understanding its complex roles and behavior in the solid state, particularly in highly correlated and magnetic materials, has grown increasingly desirable as technology demands advanced devices and materials based on ever stricter comprehension and control of the electron spin. However, direct and efficient spin dependent probes of electronic structure are currently lacking.Angle Resolved Photoemission Spectroscopy (ARPES) has become one of the most successful experimental tools for elucidating solid state electronic structures, bolstered by continual breakthroughs in efficient instrumentation. In contrast, spin-resolved photoemission spectroscopy has lagged behind due to a lack of similar instrumental advances. The power of photoemission spectroscopy and the pertinence of electronic spin in the current research climate combine to make breakthroughs in Spin and Angle Resolved Photoemission Spectroscopy (SARPES) a high priority .This thesis details the development of a unique instrument for efficient SARPES and represents a radical departure from conventional methods. A custom designed spin polarimeter based on low energy exchange scattering is developed, with projected efficiency gains of two orders of magnitude over current state-of-the-art polarimeters. For energy analysis, the 1 popular hemispherical analyzer is eschewed for a custom Time-of-Flight (TOF) analyzer offering an additional order of magnitude gain in efficiency. The combined instrument signifies the breakthrough needed to perform the high resolution SARPES experiments necessary for untangling the complex spin-dependent electronic structures central to today's condensed matter physics.

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Scanning electron microscopy with polarization analysis (SEMPA)

Cited by 256 publications

References 89 publications

Probing electric field control of magnetism using ferromagnetic resonance

Probing electric field control of magnetism using ferromagnetic resonance

Field-driven sense elements for chirality-dependent domain wall detection and storage

A New Spin on Photoemission Spectroscopy

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