Spin dynamics of Mn12-acetate in the thermally-activated tunneling regime: ac-susceptibility and magnetization relaxation

Abstract

In this work, we study the spin dynamics of Mn12-acetate molecules in the regime of thermally assisted tunneling. In particular, we describe the system in the presence of a strong transverse magnetic field. Similar to recent experiments, the relaxation time/rate is found to display a series of resonances; their Lorentzian shape is found to stem from the tunneling. The dynamic susceptibility $\chi (w)$ is calculated starting from the microscopic Hamiltonian and the resonant structure manifests itself also in $\chi (w)$. Similar to recent results reported on another molecular magnet, Fe8, we find oscillations of the relaxation rate as a function of the transverse magnetic field when the field is directed along a hard axis of the molecules. This phenomenon is attributed to the interference of the geometrical or Berry phase. We propose susceptibility experiments to be carried out for strong transverse magnetic fields to study of these oscillations and for a better resolution of the sharp satellite peaks in the relaxation rates.

22 pages, 23 figures; submitted to Phys. Rev. B; citations/references added

References in corpus (5)

• Spin Tunneling and Phonon-assisted Relaxation in Mn12-acetate
• Nuclear spin driven resonant tunnelling of magnetisation in Mn12 acetate
• Low temperature magnetic hysteresis in Mn${}_{12}$ acetate single crystals
• Crystal Field -AS_z^2 Does Not Produce One-Phonon Transitions With Delta S_z=+-2 [Comment on EPL 46, 692 (1999) by Leuenberger and Loss]
• Quantum Phase Interference in Magnetic Molecular Clusters

Cited by in corpus (9)

• Spin quantum tunneling in single molecular magnets: fingerprints in transport spectroscopy of current and noise
• 55Mn NMR in Mn12 acetate: Hyperfine interaction and magnetic relaxation of cluster
• Cross-relaxation and phonon bottleneck effects on magnetization dynamics in LiYF4:Ho3+
• Magnetic Field Effects on the Far-Infrared Absorption in Mn_12-acetate
• Solving spin quantum-master equations with matrix continued-fraction methods: application to superparamagnets
• Studies of transverse and longitudinal relaxations of ${}^{55}$Mn in molecular cluster magnet Mn${}_{12}$Ac
• Magnetic energy-level diagrams of high-spin (Mn${}_{12}$-acetate) and low-spin (V${}_{15}$) molecules
• Nonlinear response of single-molecule nanomagnets: equilibrium and dynamical
• Nonlinear ac stationary response and dynamic magnetic hysteresis of quantum uniaxial superparamagnets