We use spin-polarized scanning tunneling microscopy to demonstrate that Ho atoms on magnesium oxide exhibit a coercive field of more than 8 T and magnetic bistability for many minutes, both at 35 K. The first spontaneous magnetization reversal events are recorded at 45 K, for which the metastable state relaxes in an external field of 8 T. The transverse magnetic anisotropy energy is estimated from magnetic field and bias voltage dependent switching rates at 4.3 K. Our measurements constrain the possible ground state of Ho single-atom magnets to either Jz=7 or 8, both compatible with magnetic bistability at fields larger than 10 mT.
Bibliographical noteFunding Information:
We thank A. Singha and S. Rusponi for discussions and our mechanical and electronic workshops for expert assistance. F. D. acknowledges funding support from the Institute of Basic Science under the Project No. IBS-R027-D1. F. D. N. acknowledges support from the Swiss National Science Foundation under Project No. PZ00P2_167965.
© 2018 American Physical Society.