We identify the mechanism of energy dissipation relevant to spin-sensitive nanomechanics including the recently introduced magnetic exchange force microscopy, where oscillating magnetic tips approach surface atomic spins. The tip-surface exchange couples spin and atom coordinates, leading to a spin-phonon problem with Caldeira-Leggett type dissipation. In the overdamped regime, that can lead to a hysteretic flip of the local spin with a large spin-dependent dissipation, even down to the very low experimental tip oscillation frequencies, describing recent observations for Fe tips on NiO. A phase transition to an underdamped regime with dramatic drop of magnetic tip dissipation should in principle be possible by tuning tip-surface distance.
@article{arxiv.1010.4880,
title = {Atomic spin sensitive dissipation on magnetic surfaces},
author = {Franco Pellegrini and Giuseppe E. Santoro and Erio Tosatti},
journal= {arXiv preprint arXiv:1010.4880},
year = {2010}
}