Heavy Fermion Systems as Ternary Intermetallics with Extraordinary Properties

3 Heavy Fermion Systems as Ternary Intermetallics with Extraordinary Properties 

Heavy Fermion Systems (HFS) are particular metallic materials which contain so-called heavy electrons. The characteristic observation for these systems is that the electrons which are responsible for the electric transport possess a high effective mass. This phenomenon, however, arises at low temperatures of about 10 K. At high values, e.g. room temperature, HFS show a normal behavior. 

Heavy Fermion Systems are intermetallics which consist of rare earths or actinides together with other metal species. Examples are CeAl3 [43] and UPt3 [44]. These materials have partially filled 4/or 5/shells. At high temperatures the / electrons are localized. This behavior is comparable to conventional alloys with rare earths or actinides. With decreasing temperature the systems order in an antiferromagnetic state. Heavy Fermion Systems, however, behave like normal metals but the effective mass of the electrons is significantly enhanced (often by a factor of hundred). 

Electron spectroscopic techniques enable to determine the electronic properties in a very direct way. But, atomically clean and well-ordered surfaces are necessary for this investigation due to the surface sensitivity. Therefore, at the beginning it will be demonstrated that the evaporation of HFS on W(llO) results in samples which are suited for electron spectroscopy [45—47]. 

3 Structural and Electronic Properties of Rare Earth Metal Systems 

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