Properties of the Surface Magnetization in Ferromagnetic Crystals

Abstract

are listed in Table VII. Eq. (40) was applied to these data with the assumption that N 0 for skeleton films on chromium was the same as for normal films. The value of nw which was required to satisfy Eq. (40) when iV/iVV = 0.7510 and i = 80° was nw = 1.295. Thus the method of building films simultaneously on glass and chromium affords a useful means of making two independent determinations of nw which cover a range of i from 14° to 80°.After the data given in Tables VI and VII were obtained, films were built on seven microscope slides, each film having steps of 333, 343, 353 layers. All were soaked in benzene for 1 min. Measurement of the angles i at which these films reflected the minimum m = 7 gave the result nw-1.32. It frequently happens that after a water solution has stood in a trough for several hours the values of nw which are then obtained are slightly higher than the initial values. This is probably due to a gradual accumulation in the solution of substances dissolved from the trough or taken up from the air.A SMALL magnetic field applied normal to the polished surface of a silicon-iron single crystal will cause magnetic powder in a colloid suspension placed on it to collect into regular patterns related to the crystal symmetry. To explain these patterns, which resemble mazes with paths about 4 microns wide on a (100) surface but consist of lines parallel to a [110] The slides were stacked in a pile and the birefringence of the total of the seven films was measured by means of a quartz wedge compensator using transmitted light. The relative phase retardation of the R s and R v rays corresponded to X/4 for sodium light at i = 48° and X/3 at i = 54°. The total thickness Nt w of the 2471 layers was 59,800A, taking % = 24.2A. Therefore the factor 5752£ in Eq. (28) was replaced by 59,800. For A/=1473A at i = 48° it was found that when ^i = 1.32 the value of n 3 which gave terms which satisfied Eq. (28) was Ws = 1.390. For A/=1964A at i = 54° the calculated value was n 3 = 1.391.A measurement of Brewster's angle made after these films were built gave the result ^ = 51° 17'. Substituting i B = 51° 17' and n = 1.32 in Eq. (34) we obtain n$= 1.383. The refractive indices of the normal films built at pH = 7.0 were Wi= 1.491, » 3 = 1.551 from Eqs. (12) and (25). The skeleton films having »i=1.32 and n 3 = 1.390 or 1.383 have therefore approximately the same value of n^ -ni as the normal films.axis on a (llO) surface, McKeehan and Elmore 1 assumed the surface to contain blocks about 2 microns on a side spontaneously magnetized along <100> or <110> axes in the surface, with opposing magnetizations at about one-half 1 LThe magnetic powder patterns found on polished iron crystals (which may contain a few percent of silicon) have been studied more carefully by using a macroscopic model and by investigating the forces on the powder particles. Reasons are given for preferring one of two simple models to explain the patterns; some interesting implications of the proposed model are then considered. Experiments are descr...

Nanotextured Dynamics of a Light-Induced Phase Transition in VO2

“…Polarized light microscopy is an established approach to characterize the local orientation of structural domains in anisotropic crystalline matter. 19,20 This approach is, however, diffraction-limited, preventing the characterization of nanotextured domain patterns. SNOM can overcome the diffraction limit, but the nano-optical signal is a complicated combination of the optical responses along different crystal axes.…”

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“…Mechanical polishing was found to completely dis rupt the original domain structure by introducing mechanical stresses at the surface. By 1937» however, W. C. Elmore (8) had Introduced several Improvements in the preparation of ferromagnetic colloidal suspensions and in the use of elec trolytic polishing technique. These refinements led to rela tively true surface domain observations.…”