Electron momentum distribution in amorphous metals investigated by positron annihilation

Nuclear Instruments and Methods 199 (1982) 371 371 North-Holland Publishing Company

E L E C T R O N M O M E N T U M D I S T R I B U T I O N IN A M O R P H O U S METALS INVESTIGATED BY P O S I T R O N A N N I H I L A T I O N

K. K R I S T I A K O V A and J. K R I S T I A K Institute of Physics SA Sc, 89930 Bratislava, Czechoslovakia

P. G A L A N Institute of Preventive Medicine, Bratislava, Czechoslovakia

Abstract

Electron momentum distribution in amorphous metals and the crystalline form of NixFe80_xB20 (x = 10, 20, 30, 40) were investigated by positron annihilation. The samples were 30 mm thick ribbons, produced by rapid quenching of liquid metal on a rotating Cu wheel. The positron source was 22Na on mylar or blotting paper between two samples in sandwich arrangement. The 3,-radiation was detected by a Ge(Li) detector which has a resolution at 511.9 keV (l°6Ru) of 1.6 keV.

An unfolding method based on Bayes principle was applied to calculate the Doppler-broadening; S-parameter values were also determined.

The calculated momenturfi distributions revealed a difference for the Ni30FesoB20 sample.

THE SURFACE BORON CONCENTRATION OF NixFeso_xB2o SAMPLES

K. K R I S T I A K O V A and J. K R I S T I A K Institute of Physics SA Se, 89930 Bratislava, Czechoslovakia

J. KVITEK * and J. CERVENA Institute of Nuclear Physics, 2506 Rez near Prague, Czechoslovakia

Abstract

The boron concentration of Ni,Fes0_xB2o (x = 10, 20, 30, 40) metallic glasses was measured using the nuclear reaction l°B(nth, 4He)VLi. The samples used were 30 mm thick ribbons prepared by rapid quenching of liquid metal on a rotating Cu wheel. Irradiation was performed by the thermal beam of the INP reactor, (flux 5 × 108 n/cm2s, time of irradiation 10 min). The a-particles were detected by a Si semiconductor detector with a surface barrier. The resolution of the system was 20 keV. The boron concentration was determined from the spectrum of o~-particles (E,, = 1471 keV). The amount of boron up to 0.4 mm was found to be constant with no concentration profile. Differences in B concentration were found, viz. there were more B atoms at the surface.

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