Based on magnetic measurements, a modulated structure, as occurring in spinodal decomposition, has recently been suggested to exist in mechanically alloyed Fe-50 at.%Cu solid solutions after certain heat treatments. In this work, clear microstructural evidence of the modulated structure is obtained from transmission electron microscopy.

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The capability of scanning electron-acoustic microscopy in the characterization of MgO crystals has been studied. The conditions for the observation of different surface and subsurface features in as-grown and deformed crystals are described and the results are discussed on the basis of thermal and nonthermal mechanisms of acoustic signal generation.

Scanning electron acoustic microscopy (SEAM) has been used in the observation of domain walls in iron-and cobalt-based amorphous alloys ribbons. Controlled magnetic annealing experiments enabled the direct identification of domain walls in SEAM micrographs. Walls in perpendicular anisotropy regions of the high magnetostriction samples show a particular high contrast, probably related to the wall stress field.Scanning electron acoustic microscopy (SEAM) uses a chopped electron beam to generate an acoustic signal in the specimen surface due to the interaction between the solid and the primary electron beam.'12 This signal is usually detected by a piezoelectric transducer attached to the bottom surface of the sample and used to form a scanned image. Although in past years this technique has been ap plied to study many different materials, it has been only occasionally used to characterize magnetic materials as Fe-Si transformer sheets3 In the present work, SEAM is used to investigate the domain structure in amorphous ferromagnetic ribbons with different anisotropy and magnetostrictive properties. Such observations cannot be readily performed by conventional scanning electron microscopy techniques because very high primary energies (up to 200 keV) are necessary to obtain a high-contrast domain imageB4The magnetic behavior of the amorphous alloys is determined mainly by residual stresses which might be attributed to microstructural inhomogeneities produced during rapid quenching in its preparation.5 As a consequence, a careful field annealing of the samples was in some cases necessary in order to release internal stresses and clarify considerably the magnetic domain structure of the ribbons. This allows the observation of well-separated domain walls and makes easier the interpretation of SEAM images. Furthermore, for a better understanding of the results, SEAM micrographs were compared to those obtained by Bitter technique on the same samples.Measurements were performed in Allied Chemical Co.amorphous ribbons with high (27x 10 -6, and low (0.3 X lo-6, magnetostriction constants, whose compositions are Fe7sBt3Si9 and Co,,Fe,Ni,Mo,B,Si,,, respectively. The width of the samples ranges between 4 and 8 mm and the thickness is about 45 pm. Samples were observed as-quenched and after different magnetic annealings in order to release internal stresses and to induce easy axis in different directions. The samples were annealed at 2 10 "C for 8 min and slowly cooled for 15 min.SEAM observations were performed in a Cambridge S4-10 scanning electron microscope. The experimental arrangement used in this work has been described previ0us1y.~ A chopping system consisting of a pair of condensor plates and beam blanking electronics to create a periodically modulated beam is used. A square-wave voltage with frequencies from 40 to 240 kHz is produced by a function generator. The sound signal is detected by a piezoelectric ceramic transducer (WIT) on which the samples are clamped. The signal was detected at the reference frequency f or a...

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