Heavy-fermion antiferromagnet

YbNiAl is a heavy-fermion antiferromagnet (Schank et al. 1995), and three successive antiferromagnetic phase transitions at Tn = 5.8, 2.9, and 1.3 K were observed for YbPtAl (Drescher et al. 1998). The Neel temperature of this aluminide shows a pressure dependence. Tn is almost pressure independent in an extended range up to about 11 GPa (5.6-5.2 K) and then increases rapidly, reaching Tn =7.2K at 26.2 GPa (Drescher et al. 1998). Both aluminides show metamagnetic transitions at critical fields of 2T (YbNiAl)... 

Characteristics of heavy-fermion antiferromagnets . Symbols as in table 2, with instead of T ... 

The heavy fermion antiferromagnet Ce3Pt4lni3 (Tn = 0.95 K) exhibits imusual Kondo behavior (Hundley et al., 2001) and it has an imusually large electronic contribution to the specific heat of about 1 J/molK at the Neel temperature. Thermoelectric power and Hall effect... 

At low temperatures, there are at least two ways in which the f electrons, and their magnetic moments, behave either they order spontaneously in ferromagnetic, antiferromagnetic or complicated magnetic structures, or the f electrons can form a heavy fermion state, strongly correlated with the conduction electrons. 

The existence of strong antiferromagnetic correlations in heavy fermion metals has been confirmed by extensive neutron scattering studies ( 5), and these correlations are now thought to be responsible for both the large mass renormalizations and exotic superconductivity... 

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). 

In chapter 98, Julian Sereni adds significantly to an evaluation of systematic, experimental low-temperature studies of the ambivalent behaviors of cerium (ferromagnetism, antiferromagnetism, spin glass, superconductivity, valence fluctuations, heavy Fermion, Kondo and spin fluctuations) which depend upon its environment in materials. The systematic conclusions arrived at should provide new data against which the theory can be advanced. 

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