Magnetic properties of Dy nano-islands on graphene

Abstract

We have determined the magnetic properties of epitaxially grown Dy islands on graphene/SiC(0001) that are passivated by a gold film (deposited in the ultra-high vacuum growth chamber) for {\it ex-situ} X-ray magnetic circular dichroism (XMCD). Our sum-rule analysis of the Dy $M_{4,5}$ XMCD spectra at low temperatures ($T=15$ K) as a function of magnetic field assuming Dy$^{3+}$ (spin configuration $^6H_{15/2}$) indicate that the projection of the magnetic moment along an applied magnetic field of 5 T is 3.5(3) $\mu_B$. Temperature dependence of the magnetic moment (extracted from the $M_5$ XMCD spectra) shows an onset of a change in magnetic moment at about 175 K in proximity of the transition from paramagnetic to helical magnetic structure at $T_{\rm H} =179$ K in bulk Dy. No feature at the vicinity of the ferromagnetic transition of hcp bulk Dy at $T_{\rm c}$ = 88 K is observed. However, below $\sim$130 K, the inverse magnetic moment (extracted from the XMCD) is linear in temperature as commonly expected from a paramagnetic system suggesting different behavior of Dy nano-island than bulk Dy

Intercalated rare-earth metals under graphene on SiC

“…Since Gd 3+ has the same electron configuration as Eu 2+ , their XMCD sum rules are the same resulting in an expected orbital moment, L Z = 0, , and a total moment, M total , which is equal to twice the spin moment, S Z . [29]. The field dependence shown in Fig.…”

Tuning the Magnetic Anisotropy of Lanthanides on a Metal Substrate by Metal–Organic Coordination

“…Expectation values of orbital 〈 L Z 〉 and effective spin 〈 S zeff 〉 = 〈 S z 〉 + 3〈 T z 〉 moments in units of ћ were calculated using sum rules [ 30,31 ] with the quantum numbers c = 2 and l = 3, and the number of holes n H = 5 for Dy 3+ . [ 45 ] The spin moment 〈 S z 〉 was separated from the dipole contribution 〈 T z 〉 assuming the theoretical value for Dy 3+ . [ 46 ] The total magnetic moment per atom was also calculated in μ B , M T = 2〈 S z 〉 + 〈 L z 〉.…”

Intercalated europium metal in epitaxial graphene on SiC

“…The XMCD signal is obtained from the difference between two XAS spectra of the left-and right-handed helicities, µ + and µ − . More details on data reduction is provided elsewhere [21]. We note that our intercalated samples are removed from the ultra-high vacuum chamber and transported in air for the XMCD experiments.…”