Dissipation in macroscopic magnetization tunneling

The effect of magnetoelastic dissipation upon the tunneling and coherence of the total magnetization in small (∼100 Å) single-domain ferromagnetic particles is investigated. Such tunneling would be an example of a macroscopic quantum phenomenon. It is shown that the dissipation has a super-Ohmic spectral density, J(ω)∼${\omega }^3$, and that the dissipation is weak for reasonable material parameters. Corrections to the rates, and the damping rate for coherent oscillations are obtained. A key feature is the inclusion of the elastic waves in the medium surrounding the particle.