Circular dichroism and angular deviation in x-ray absorption spectra of Dy2ScN@C80 single-molecule magnets on h−BN/Rh(111)

Abstract

Endohedral fullerenes, such as Dy2ScN@C80, are single-molecule magnets with long relaxation times of their magnetization. An open and anisotropic 4f electron shell in the lanthanides (here Dy) imposes a magnetic moment that maintains its orientation at liquid-helium temperatures for macroscopic times. If these molecules shall be used as single-bit information storage elements or for quantum operations, the orientation of the endohedral units and the orientation of the magnetic moments has to be controlled. X-ray absorption spectroscopy (XAS) and magnetic circular dichroism (XMCD)—with variation of the angle of x-ray incidence—allows for the detection of these two structural elements. We present XMCD data of Dy2ScN@C80 on an h−BN/Rh(111) nanomesh that display at 2 K a large hysteresis with a coercive field of 0.4 T. The angular dependence of the XAS data at the Dy M5 edge indicates partial ordering of the endohedral units. In order to quantify anisotropic orientation we introduce the “deviation” D as an operational quantity that measures differences between two spectra.