Observation of Magnetic Head Fields Using Distorted Transmission Electron Microscopy Images

Abstract

Density functional theory calculations on Ybusing the Hartree Fock system and the analogous Dirac-Hartree-Fock methods predict that Ybis stable in the Py,z state. The electron affinity obtained after the correlation energy functionals used are calibrated against Caand Lu is 2f 1 mHartree (54+ 27 meV).The calculations indicate that the Pilz state is unlikely to be bound due to spin-orbit coupling reducing its binding energy.It had long been thought that atoms with closed subshells such &s Ca, Sr, Ba and Ra (whose closed valence subshells are n s ' , n = 4, 5, 6 and 7), could not bind an extra electron to form a stable negative ion. With the predictions of stable Ca-, Sr-, Ba-and Ra-from a variety of theoretical methods by Froese Fischer et a/ (1987, to be referred to as FFLV), Vosko et al (i989, to be referred to as VLM), Froese Fischer (1989) and Kim and Greene (1989), and the subsequent observation by Pegg e l a/ (1987) and Garwan et a/ (1990) of the first three, this view was forced to be abandoned. As emphasized by VLM, the crucial new ingredient in the theoretical work was the extra electron going into an n.p orbital instead of following the usual trend of occupying the same orbital as the neutral atom with one higher atomic number. (In these cases this trend would place the extra electron in the (n -1)d orbital. The deviation from this pattern was observed by Feigerle et a/ (1981) who found that Sc-and Yhave the configurations [Ar]4s24p1 and [Kr]5s25p1, respectively.) To date, this np occupancy has only been confirmed for Ca-where the electron affinity (EA = 43 & 7 meV = 1.6 zk 0.25 mHartree) and configuration ([Ar]4s24p' 'PO) have been determined experimentally by Pegg et al (1987). A natural question that arises is whether there are any other closed-subshell atoms that have stable negative ions. Kim and Greene (1989) thought that the most plausible candidates were Zn-, Cdand Hg-, but concluded that the 'Po states of these ions are unlikely to be stable and suggested that the heavier alkaline earths may be the only closed-subshell atoms whose negative ions are stable. They did not consider Yb, however; a n atom with closed subshells (i.e. [Xe]4f146sZ) near the end of the lanthanide series and thus easily t Supported in part by the Natural Sciences and Engineering Resemh Council of Canada and the Ontario Centre for Large Scde Computation.

Parallel Mode Differential Phase Contrast in Transmission Electron Microscopy, I: Theory and Analysis

“…One advantage of the TIE method is that it may be used to recover the information on the phase beyond the sample, thus giving it the ability to map stray fields. Stray fields may also be measured in the TEM-DPC method, but only when they exist over a suitable substrate material, or where the microscope is modified to incorporate a patterned film or mask (Suzuki et al, 1997, 2000; Shimakura et al, 2003; Sasaki et al, 2010).…”

“…This was understood in some of the earliest work on quantifying the magnetization distribution of samples from their induction in a TEM (Fuller & Hale, 1960), but direct use of the real-space deflection information has been rare in the decades since then. Indeed, only a small number of reports of its use have been made, and these used a modified TEM, where a patterned film or shadow mask was incorporated to allow stray magnetic (Wade, 1976; Suzuki et al, 1997, 2000; Shimakura et al, 2003) and electric (Sasaki et al, 2010) fields to be mapped in vacuum. When used in tomographic applications, this technique has been labeled “projected electron magnetic tomography” (PEMT; Shimakura et al, 2003).…”

Parallel Mode Differential Phase Contrast in Transmission Electron Microscopy, II: K2CuF4 Phase Transition

“…The technique, which we refer to as TEM-differential phase contrast (TEM-DPC), has origins dating back decades (Fuller & Hale, 1960), but has gone largely unused since then. In part, this is because previous approaches have used patterned films or shadow masks to form texture suitable for assessing the image distortions, which required a modification of the microscope and limited mapping to stray magnetic (Wade, 1976;Suzuki et al, 1997Suzuki et al, , 2000Shimakura et al, 2003) and electric fields (Sasaki et al, 2010) beyond the sample. Another reason is the tremendous success since its early adoption in electron microscopy (Bajt et al, 2000;De Graef & Zhu, 2001) of methods for phase recovery through solving the transport-of-intensity equation (TIE) (Teague, 1983).…”

Parallel mode differential phase contrast in transmission electron microscopy, II: K$_2$CuF$_4$ phase transition

“…The technique, which we refer to as TEMdi erential phase contrast (TEM-DPC), has origins dating back decades (Fuller & Hale, 1960), but has gone largely unused since then. In part, this is because previous approaches have used pa erned films or shadow masks to form texture suitable for assessing the image distortions, which required modification of the microscope and limited mapping to stray magnetic (Wade, 1976;Suzuki et al, 1997;Suzuki et al, 2000;Shimakura et al, 2003) and electric fields (Sasaki et al, 2010) beyond the sample. Another reason is the tremendous success since its early adoption in electron microscopy (Bajt et al, 2000;De Graef & Zhu, 2001) of methods for phase recovery through solving the transport-of-intensity equation (TIE) (Teague, 1983).…”