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arXiv · 1111.1399

Chemically-Mediated quantum criticality in NbFe_2

Aftab Alam·D. D. Johnson
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Abstract

Laves-phase Nb{1+c}Fe_{2-c} is a rare itinerant intermetallic compound exhibiting magnetic quantum criticality at c_{cr}=1.5%Nb excess; its origin, and how alloying mediates it, remains an enigma. For NbFe_2, we show that an unconventional band critical point (uBCP) above the Fermi level E_F explains most observations, and that chemical alloying mediates access to this uBCP by an increase in E_F with decreasing electrons (increasing %Nb), counter to rigid-band concepts. We calculate that E_F enters the uBCP region for c_{cr} > 1.5%Nb and by 1.74%Nb there is no Nb site-occupation preference between symmetry-distinct Fe sites, i.e., no electron-hopping disorder, making resistivity near constant as observed. At larger Nb (Fe) excess, the ferromagnetic Stoner criterion is satisfied.

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Aftab Alam, D. D. Johnson. 2011-11-06. Chemically-Mediated quantum criticality in NbFe_2. https://doi.org/10.1103/physrevlett.107.206401

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