We have synthesized Co fine particles with the average diameter (D) of less than 500 Å by sputtering Co in a somewhat high inert-gas pressure. It has been found that there is a close relationship between the particle size and the crystal phase; that is, pure fcc ͑␤͒ phase for Dр200 Å, a mixture of hcp ͑␣͒ and ␤ phases for D ϳ300 Å, and ␣ phase with inclusion of a very small amount of ␤ phase for Dу400 Å. Precise structural characterizations have revealed that the ␤ particles are multiply twinned icosahedrons and the ␣ particles are perfect single crystals with external shape of a Wulff polyhedron. In order to explain the size effect on the crystal phase of Co fine particles, we have performed theoretical calculations for total free energies of an ␣ single crystal, a ␤ single crystal, and a multiply twinned ␤ icosahedron. The present calculations well explain the size dependence of the crystal phase of the Co fine particles, and have revealed that the stabilization of ␤ phase, confirmed by previous studies, is the intrinsic effect caused by the small dimensionality of fine particles. Moreover, the phase transformations that occurred in annealing experiments can also be explained by the theory. ͓S0163-1829͑97͒05145-X͔

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Magnetic properties such as magnetization, coercivity, and magnetostriction of rapidly quenched ternary Fe~oo--2--yAlzSiy (0 5 x 5 28.3, 0 5 y 5 lo), Feloo--o--yAlzBy, and Feeloo-zA1,Gey (0 2 x 5 28.3, 0 5 y 5 20.4) are investigated. I n the Fe-Al-Si system, the alloys near Fe,Al,, composition exhibit relatively soft magnetic properties. In the Fe-Al-B system, amorphous structure is achieved in the range 12 5 y 5 25 and best soft magnetic properties, H, = 1.6 A/m, Bs = 1.1 T, pm = 1.4 x lo5, e = 160 pi2 cm are obtained around Fe,,,Al,B,, composition. I n the Fe-Al-Ge system, magnetostriction is nearly zero in the composition range 0 5 x 5 15, 10 5 5 y 5 15. The Fe-rich alloys in Fe-Al-Si and Fe-Al-Ge systems show a high saturation induction above 2.0 T and a small magnetostriction less than 10 x Magnetisohe Eigenschaften, wie Magnetisierung, Koerzitivkraft und Magnetostriktion, von schnell abgeschrecktem, terniirem Feloo-2-vA1,Si-y (0 5 x 5 28,3, 0 5 y 5 lo), FelOo--z--yA1zBy und Feloo-zA1,Gey (0 5 5 5 28,3, 0 5 y 5 20,4) werden untersucht. Im Fe-Al-Si-System zeigt die Legierung in der Niihe der Fe,,Al,,-Zusammensetzung relativ weiche megnetische Eigenschaften. Im Fe-Al-B-System wird die amorphe Struktur im Bereich 12 5 y 5 26 erreicht, und die weichmagnetischen Eigenschaften, H, = 1,6 A/m, B, = 1,l T, pm =

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X-ray diffraction measurements have been performed to investigate a crystal structure of a precipitation phase in oxygen-reduced Nd 1:85 Ce 0:15 CuO 4þy (NCCO). A detailed structure analysis of the precipitation phase as well as the parent NCCO phase revealed that the precipitation phase is a cubic (Nd,Ce) 2 O 3 , which is distorted tetragonally by the surrounding NCCO phase. The averaged grain size of the precipitation phase exceeds 200A parallel to the CuO 2 plane of the parent NCCO, while the size along layered direction is short-ranged ($30 A). The grain thickness along layered direction is strongly correlated with the homogeneity of superconducting state. The volume fraction of the (Nd,Ce) 2 O 3 phase is about 2%. We also performed electron diffraction as well as microscopy experiment, which confirms that the (Nd,Ce) 2 O 3 phase segregate from the parent NCCO phase and exists as an epitaxial layer along the c-axis.