Thermodynamics and equations of motion for quantum spin crystals

Hamiltons’s approach is used for obtaining nonlinear dynamic equations for a quantum spin crystal. The second law of thermodynamics is formulated. Expressions for flux densities of additive integrals of motion are derived in terms of thermodynamic potential density both for Galilean-invariant and Galilean-noninvariant systems. Time-independent solutions corresponding to helical magnetic ordering are obtained. The nonuniformity of the magnetic field is taken into account in dynamics equations.

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