  Atomistic-continuum multiscale modelling is becoming an increasingly popular
tool for simulating the behaviour of materials due to its computational
efficiency and reliable accuracy. In the case of ferromagnetic materials, the
atomistic approach handles the dynamics of spin magnetic moments of individual
atoms, while the continuum approximations operate with volume-averaged
quantities, such as magnetisation. One of the challenges for multiscale models
in relation to physics of ferromagnets is the existence of the long-range
dipole-dipole interactions between spins. The aim of the present paper is to
demonstrate a way of including these interactions into existing
atomistic-continuum coupling methods based on the partitioned-domain and the
upscaling strategies. This is achieved by modelling the demagnetising field
exclusively at the continuum level and coupling it to both scales. Such an
approach relies on the atomistic expression for the magnetisation field
converging to the continuum expression when the interatomic spacing approaches
zero, which is demonstrated in this paper.
