Unconventional Spin Relaxation Involving Localized Vibrational Modes in Ho Single-Atom Magnets

Abstract

We investigate the spin relaxation of Ho single atom magnets on MgO=Agð100Þ as a function of temperature and magnetic field. We find that the spin relaxation is thermally activated at low field, while it remains larger than 1000 s up to 30 K and 8 T. This behavior contrasts with that of single molecule magnets and bulk paramagnetic impurities, which relax faster at high field. Combining our results with density functional theory, we rationalize this unconventional behavior by showing that local vibrations activate a twophonon Raman process with a relaxation rate that peaks near zero field and is suppressed at high field. Our work shows the importance of these excitations in the relaxation of axially coordinated magnetic atoms.

Influence of 4f filling on electronic and magnetic properties of rare earth-Au surface compounds

“…This is of major interest in materials exhibiting competing magnetic and electronic phases around quantum critical points, such as heavy-fermion metals 12 . Specially the Ho case is of recent interest due to its high angular magnetic moment and its unconventional magnetic properties [13][14][15][16] .…”

Correlation between Electronic Configuration and Magnetic Stability in Dysprosium Single Atom Magnets

“…Magnetic relaxation at lower fields becomes too fast to be detected with our setup. The lifetime of 4f 10 Dy atoms on MgO is a few orders of magnitude shorter than that reported for 4f 9 Dy top on 2 ML MgO/Ag(100) 8 , and for other Ho and Dy single atom magnets with the same 4f occupation 3,12,43 , but similar to that of divalent Dy 4f 9 5d 1 single molecule magnets in polycrystalline form 22 .…”

“…To quantify the lifetime of the 4f 10 Dy top , we record the time decay of the XMCD signal at constant external field after saturating the magnetization in a field of 3 T prior to switching the field to the indicated values and starting the acquisition 3,4,18,40,42,43 . Figure 4b shows the magnetic relaxation at three different external fields, with the asymptotic value of the XMCD signal indicating the corresponding equilibrium magnetization of the ensemble.…”

Dysprosium magnesium silicate apatite featuring field and temperature stable slow magnetization relaxation

“…Very recently the suppression of the Raman process was proposed to guide the relaxation of magnetic moment of a Ho lone atom attached to the MgO surface. 37 Whereas under low magnetic eld the relaxation was fast and thermally activated, under a eld of 80 kOe it remained very slow exceeding 10 3 s at temperatures up to 30 K. It was rationalized by DFT calculations considering a Raman process involving local molecular vibrations.…”