Magneto-elastic waves in crystals of magnetic molecules

We study magneto-elastic effects in crystals of magnetic molecules. Coupled equations of motion for spins and sound are derived and the possibility of strong resonant magnetoacoustic coupling is demonstrated. Dispersion laws for interacting linear sound and spin excitations are obtained for bulk and surface acoustic waves. We show that ultrasound can generate the magnetization wave and that the decay of the inverse population of spin levels can generate ultrasound. Alternatively, the decay of the inverse population of spin levels can generate ultrasound. Possibility of solitary waves of the magnetization accompanied by the elastic twists is demonstrated.

Figure 1

(Color online) Interacting sound and spin modes. Notice the gap below spin resonance ${\omega }_0$.

Figure 2

(Color online) Geometry of the problem with surface acoustic waves.

Figure 3

(Color online) Magnetization inside the soliton as a function of $\xi$ for $W=0$.