Amorphous Fe-B alloys in B-Fe-Ag multilayers studied by magnetization and Moessbauer measurements

• Published in: Journal of alloys and compounds Vol. 509; pp. S188 - S192
• Main Authors: Kiss, L F, Balogh, J, Bujdoso, L, Kaptas, D, Kemeny, T, Kovacs, A, Vincze, I
• Format: Journal Article
• Language: English
• Published: 01.06.2011
• Subjects: Crystal structure; Ferrous alloys; Iron; Magnetic properties; Magnetization; Multilayers; Silver
• ISSN: 0925-8388
• DOI: 10.1016/j.jallcom.2010.11.014

Bulk and local magnetic properties were studied in [1 nm B + 1 nm [super]57Fe + x nm Ag] sub(5), x = 1, 2, 4, 5 and 10, multilayer samples. Although Ag does not mix with either of the other two elements the magnetic properties of the multilayers are strongly influenced by the Ag thickness below x = 5, whereas no such effect is observed above this value. The Moessbauer measurements indicate a complete amorphization of the thin Fe layers in each sample, as a result of intermixing with the B layers. The variation of the magnetic properties is explained by the variation of the average B concentration of the amorphous Fe-B layers, which depends on the thickness of the Ag barrier layers. The magnetization measurements indicate ferromagnetic behaviour of the ultra-thin amorphous layers with the presence of less than 10% superparamagnetic moments for x = 5 and 10. The average B concentration of the amorphous Fe-B alloy, as estimated from the Fe hyperfine fields, is around 40 at%. It is significantly lower than the 60 at% nominal B concentration, suggesting the presence of an unalloyed B layer, as well. This picture is supported by transmission electron microscopy investigations which reveal two amorphous layers of different B concentration in between the crystalline Ag layers.