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Abstract

It is generally believed that both the spin fluctuations and the atomic vibrations are important for the finite-temperature properties of magnetic transition metals. Here we proposed a spin-lattice fluctuation theory which is a combination of the spin fluctuation theory and the conventional tight-binding model for non-magnetic materials. A Hamiltonian Monte Carlo algorithm is then developed to solve this model numerically. The first pronounced effect we observed is that the atomic vibrations significantly decrease the Curie temperature. Besides, we observed strong phonon softening in BCC iron, which is induced by spin fluctuations, and found that the phonon-phonon interaction is crucial to stabilize the delta-iron dynamically.