Exchange constants for local spin Hamiltonians from tight-binding models

8 Mar 2021  ·  Simon Streib, Attila Szilva, Vladislav Borisov, Manuel Pereiro, Anders Bergman, Erik Sjöqvist, Anna Delin, Mikhail I. Katsnelson, Olle Eriksson, Danny Thonig ·

We consider the mapping of tight-binding electronic structure theory to a local spin Hamiltonian, based on the adiabatic approximation for spin degrees of freedom in itinerant-electron systems. Local spin Hamiltonians are introduced in order to describe the energy landscape of small magnetic fluctuations, locally around a given spin configuration... They are designed for linear response near a given magnetic state and in general insufficient to capture arbitrarily strong deviations of spin configurations from the equilibrium. In order to achieve this mapping, we include a linear term in the local spin Hamiltonian that, together with the usual bilinear exchange tensor, produces an improved accuracy of effective magnetic Weiss fields for non-collinear states. We also provide examples from tight-binding electronic structure theory, where our implementation of the calculation of exchange constants is based on constraining fields that stabilize an out-of-equilibrium spin configuration. We check our formalism by means of numerical calculations for iron dimers and chains. read more

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Materials Science Strongly Correlated Electrons