Binary Alloys of Rare Earth and Transition Metals

2 Binary Alloys of Rare Earth and Transition Metals 

In this section the determination of the growth behavior of thin GdFe2 films on W(llO) is presented. It will be shown that an epitaxial growth of up to two monolayer thick films is possible. Based on the atomically resolved STM images 

3 Structural and Electronic Properties of Rare Earth Metal Systems 

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The existence of several intermetallic compounds of composition MX2 to MX5 have been reported in binary systems containing rare earth or actinide elements (M) with transition metals (X). The brittle alloys were found to be hexagonal or rhombo-hedral and to belong to the M + iXs 1 series formed by the stacking of M2X4 blocks... 

Figure 10 presents the Curie temperature (Tc) vs the TM-content (x) for Co- and Fe-based binary alloys. Alloying rare-earth elements with small amounts of transition metals (x < 0.2) leads to a decrease in Curie temperature. This is particularly obvious in the Gd—Co system where it corresponds to a nonmagnetic dilution similar to that of Cu (41,42). This indicates that TM atoms experience no exchange coupling unless they are surrounded by a minimum number j of other TM atoms. The critical number is j = 5 for Fe and j = 7 for Co. The steep increase of Tc for Co-based alloys with x about 0.7 is based on this effect. 

It was previously shown that rapidly solidified Al-RE and Al-TM-RE alloys (RE is rare earth metal or yttrium, TM is transition metal) have amorphous structure in relatively wide range of compositions and alloying elements [1], Similarly to rare earth metals and Y, Sc belongs to the IIIB group of the Periodic Table of Elements, but we have found no data on the influence of Sc on the formation of amorphous structure in A1 alloys in the literature. On the other hand, Sc is known for a many-sided improving action on many crystalline A1 alloys [2], The aim of this work was to investigate the effect of Sc on the structure and mechanical properties (hardness) of rapidly solidified binary Al-Sc alloys as well as of Al-Ce-Sc and Al-Ni-Ce-Sc amorphous alloys. 

The numerous glass-forming binary alloys may be divided into two main categories metal-metal alloys and metal-metalloid alloys. The former category may again be subdivided into three subgroups comprising alloys of transition metals (3d, 4d, 5d), alloys of simple metals and alloys of transition metals with either rare earths... 

Lundin (1970), in an investigation of the formation of samarium-type structure in intra rare earth binary alloys included six compositions in the lanthanum-scandium system ranging from 10 to 85at% La. Lundin prepared his alloys using 99.8(wt )% pure lanthanum metal (major impurities, 330 ppm other rare earths, 510 ppm O, 50 ppm each Si, Mg and Zn) and 99 -F (wt )% pure scandium for which there were no details given on the impurities. Lundin found two-phase inuniscibility at low temperatures in the lanthanum-scandium system and, since no samarium-type structure was found, he concluded that scandium behaves more like the neighboring transition elements than it does as a rare earth metal. 

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