2007/09/30 by Ioannis Rousochatzakis
Chemistry · Materials Science · Physics and Astronomy · #Advanced NMR Techniques and Applications #Anisotropy #Condensed matter physics #Decoupling (probability) #Isotropy #Magnetic field #Magnetic properties of thin films #Magnetism in coordination complexes #Magnetization #Microscopic theory #Nanomagnet #Omega #Physics #Quantum mechanics #cond-mat.mes-hall #cond-mat.other
paper · pdf · doi:10.1103/physrevb.76.214431
published as Phys. Rev. B 76, 214431 (2007) · 7 pages
arxiv created 2007/10/29 · openalex publication_date 2007/12/27 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
We present a microscopic theory for the phonon-driven decay of the magnetization fluctuations in a wide class of nanomagnets where the dominant energy is set by isotropic exchange and/or uniaxial anisotropy. Based on the Zwanzig-Mori projection formalism, the theory reveals that the magnetization fluctuations are governed by a single decay rate \ensuremathωc, which we further identify with the zero-frequency portion of the associated self-energy. This dynamical decoupling from the remaining slow degrees of freedom is attributed to a conservation law and the discreteness of the energy spectrum and explains the omnipresent monoexponential decay of the magnetization over several decades in time, as observed experimentally. A physically transparent analytical expression for \ensuremathωc is derived which highlights the three specific mechanisms of the slowing-down effect which are known so far in nanomagnets.