Growth morphology and magnetic properties of Gd adatoms on h-BN template: From single atom to small cluster and monolayer

Abstract

Atomic assembly of surface-supported nanostructures with high structural stability, large magnetic moment and magnetic anisotropy energy (MAE) hold great potential applications in spintronic and magnetic storage devices. With the changes of deposition coverage of Gd adatoms on the hexagonal boron nitride (h-BN) template, we systemically investigate the low-lying structures and magnetic properties of Gdn (n=1–19) clusters and monolayers (1ML-Gd and 2ML-Gd) by combining various theoretical methods including the spin–orbital coupling (SOC) density functional theory (DFT), abinitio molecular dynamics (AIMD) simulations and lattice dynamical calculations. Favorable adsorption sites and preferable orientations as well as distinguishing electronic structures have been thoroughly explored to reveal the bonding characteristics and growth models of Gd clusters and thin films. We demonstrate that the planar Gd clusters/monolayers deposited on h-BN surface can exhibit the energetically, dynamically, thermally, and thermomagnetically stable at high temperature of 500 K. The Gd-B covalent and ionic bonding interactions instead of Gd-N interactions give the synergetically contributions for stabilizing small clusters on planar h-BN sheet via the hybridizations of Gd-5d and B-2pz orbitals, while Gd-N covalent bonds participate in additionally bonding interaction for the depositions of large clusters on corrugated h-BN sheet due to the transformations from B/N-sp2 to B/N-sp3 hybridizations. Robust ferromagnetic (FM) couplings with large spin magnetic moments about 7.6 μB per Gd atoms are always found to be the ground states. Orbital magnetic moments of −0.10∼−0.37 μB per atom and large MAEs in few meV are primarily contributed by Gd-5d electrons. We propose that the Ruderman–Kittel–Kasuya–Yosida (RKKY) interaction mediated by 5d electrons determines the long-term FM coupling between Gd atoms, and we estimate the Curie temperatures ranging from 150 K to 60 K for different Gd deposited systems. The excellent structural and magnetic stability as well as large magnetic moment and MAEs therefore facilitate Gd cluster and thin film the promising candidates for spintronic applications.