Effect of magnetism on lattice dynamical properties in the Ni–Cu alloy from first principles

• Magnetic order has subtle influence on phonon modes, mostly on longitudinal ones.
• Dynamical couplings of first- and second-NN bonds are quite changed by magnetism.
• Structural and chemical modifications are dominating the first-NN coupling.
• Changes in the second-NN coupling originate solely from the magnetic order.

We have studied the lattice dynamical properties of the magnetic intermetallic Ni1−xNi1−xCux alloy within the framework of density functional perturbation theory using a mixed-basis pseudopotential method and the self-consistent virtual crystal approximation for modeling the alloy. A transition from a ferromagnetic (FM) to a non-magnetic (NM) state is found at a critical concentration xc=0.45. Phonon spectra as a function of x   for both FM and NM states obtained for the entire range of Cu content show good agreement with available experimental data. The magnetic order for x