These three metallic systems do not exhibit any magnetic ordering despite experiments show the existence of localized moments with large antiferromagnetic exchange: this is a consequence of the strong geometric frustration (Y(Sc)Mn_{ 2} and LiV_{ 2}O_{ 4} have the Pyrochlore structure, while beta-Mn has a more complicated frustrated structure). Another common feature is their very large specific heat coefficient \gamma =C/T (420 mJ mole^{ -1} K^{ -2} for LiV_{ 2}O_{ 4}). Several explanations have been proposed for this ''3d heavy fermion behavior'', including a 3d-Kondo effect. However the similarities between the three compounds indicate that frustration plays a big role. We propose a new model which takes into account the existence of two types of 3d-electrons (localized and itinerant) and a frustrated antiferromagnetic exchange between the localized 3d electrons.
Categories: cond-mat.str-el