Near coincidence of metal-insulator transition and quantum critical fluctuations: Electronic ground state and magnetic order in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>Fe</mml:mi><mml:mrow><mml:mn>1</mml:mn><mml:mo>−</mml:mo><mml:mi>x</mml:mi></mml:mrow></mml:msub><mml:msub><mml:mi>Co</mml:mi><mml:mi>x</mml:mi></mml:msub><mml:mi>Si</mml:mi></mml:mrow></mml:math>
J. Grefe, P. Herre, Y. Hilgers, F. Labbus, N. Lüer-Epping, N. Radomski, M.A.C. de Melo, F. J. Litterst, Dirk Мenzel, S. Süllow
Abstract
We present a detailed study of the electronic and magnetic ground-state properties of ${\mathrm{Fe}}_{1\ensuremath{-}x}{\mathrm{Co}}_{x}\mathrm{Si}$ using a combination of macroscopic and microscopic experimental techniques. From these experiments we quantitatively characterize the metal-insulator transition and magnetic/nonmagnetic quantum phase transition occurring at low-doping levels in ${\mathrm{Fe}}_{1\ensuremath{-}x}{\mathrm{Co}}_{x}\mathrm{Si}$. From our study, we find a surprising closeness of the critical composition of the metal-insulator transition at ${x}_{\mathrm{MIT}}=0.014$ and the quantum phase transition at ${x}_{\mathrm{LRO}}\ensuremath{\sim}0.024\ensuremath{-}0.031$. This suggests that these effects are cooperative and depend on each other.