Onset of magnetism in concentrated ternary alloys I

The onset of magnetism and the magnetic propreties of concentrated substitutional ternary alloys A(Fe_1?xB_x)₂ (A = Y, Zr, U; B = Mn, Co, Ni and Al), Y₂(Ni_1?xCo_x)₇, Y(Ni_1?xCo_x)₃, Y₆(Fe_1?xMn_x)₂₃ and Ti(Fe_1?xCo_x) as well as the amorphous alloy system (Fe_1?xNi_x)₇₇Si₁₀B₁₃ are discussed in terms of homogeneous and heterogeneous models based on the Stoner-, Edwards- Wohlfa arth- and the Landau theory of phase transitions of second order. For a detailed comparison of the nine ternary systems A(Fe, B)₂ (A = Y, Zr, U; B = Mn, Co, Al) we refer to a following paper. From the results obtained on alloying UNi₂ with Fe, Co and Cu we propose that the magnetic moment of UNi₂—contrary to UFe₂—resides mainly on U rather than on the Ni site. The appearance of magnetism in YNi_x compounds by either changing the Y : Ni ratio or substituting Ni by Co in YNi₃ and Y₂Ni₇ is mainly attributed to band effects for which a schematic N(E) curve is proposed. The breakdown of long-range magnetic order in Y₆(Fe, Mn)₂₃ seems to be caused by a lack of delocalized electrons and a preferential site occupation of Mn and Fe. The magnetic properties of Ti(Fe_1?xCo_x) change from an itinerant to a localized moment behaviour above and below x = 0.5 due to the occurrence of Fe antistructure atoms which drive the onset of long-range magnetic order. The occurrence of magnetism in amorphous alloys compared with that of crystalline alloys with a high degree of disorder may be characterized in a similar way.