title: Magnetic Hysteresis in Er Trimers on Cu(111).
abstract: We report magnetic hysteresis in Er clusters on Cu(111) starting from the size of three atoms. Combining X-ray magnetic circular dichroism, scanning tunneling microscopy, and mean-field nucleation theory, we determine the size-dependent magnetic properties of the Er clusters. Er atoms and dimers are paramagnetic, and their easy magnetization axes are oriented in-plane. In contrast, trimers and bigger clusters exhibit magnetic hysteresis at 2.5 K with a relaxation time of 2 min at 0.1 T and out-of-plane easy axis. This appearance of magnetic stability for trimers coincides with their enhanced structural stability.
authors.affiliation: Institute of Physics, École Polytechnique Fédérale de Lausanne , Station 3, CH-1015 Lausanne, Switzerland.
authors.forename: Aparajita
authors.initials: A
authors.lastname: Singha
authors.affiliation: Institute of Physics, École Polytechnique Fédérale de Lausanne , Station 3, CH-1015 Lausanne, Switzerland.
authors.forename: Fabio
authors.initials: F
authors.lastname: Donati
authors.affiliation: Institute of Physics, École Polytechnique Fédérale de Lausanne , Station 3, CH-1015 Lausanne, Switzerland.
authors.forename: Christian
authors.initials: C
authors.lastname: Wäckerlin
authors.affiliation: Institute of Physics, École Polytechnique Fédérale de Lausanne , Station 3, CH-1015 Lausanne, Switzerland.
authors.forename: Romana
authors.initials: R
authors.lastname: Baltic
authors.affiliation: Institute of Physics, École Polytechnique Fédérale de Lausanne , Station 3, CH-1015 Lausanne, Switzerland.|Swiss Light Source, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland.
authors.forename: Jan
authors.initials: J
authors.lastname: Dreiser
authors.affiliation: Institute of Physics, École Polytechnique Fédérale de Lausanne , Station 3, CH-1015 Lausanne, Switzerland.
authors.forename: Marina
authors.initials: M
authors.lastname: Pivetta
authors.affiliation: Institute of Physics, École Polytechnique Fédérale de Lausanne , Station 3, CH-1015 Lausanne, Switzerland.
authors.forename: Stefano
authors.initials: S
authors.lastname: Rusponi
authors.affiliation: Institute of Physics, École Polytechnique Fédérale de Lausanne , Station 3, CH-1015 Lausanne, Switzerland.
authors.forename: Harald
authors.initials: H
authors.lastname: Brune
keywords: Rare earth clusters; X-ray magnetic circular dichroism; hysteresis; magnetic anisotropy; scanning tunneling microscopy; superlattice