Tuning the 4f-state occupancy of cerium in highly correlated CeSi/ Fe multilayers: a study by x-ray absorption spectroscopy

TL;DR

This study investigates how the 4f electron occupancy in cerium within CeSi/Fe multilayers can be tuned by silicon content, revealing the interplay of hybridization, exchange interactions, and magnetic order mechanisms through x-ray absorption spectroscopy.

Contribution

It provides new insights into the electronic and magnetic structure of Ce in multilayers, highlighting the role of Si content in modulating 4f occupancy and magnetic interactions.

Findings

Increasing Si reduces 4f hybridization and enhances 4f magnetic polarization.

Exchange interactions between Ce-4f and 5d electrons are crucial at high Si.

Different mechanisms drive magnetic order depending on Si concentration.

Abstract

Spectra of x-ray absorption and magnetic circular dichroism were measured at M4,5(3d) and L2,3(2p) edges of Ce in multilayers [Ce(1-x)Six/Fe]xn, with x between 0.1 and 0.65. The study uncovers the highly correlated nature of this layered system. An alpha-phase like electronic configuration of Ce is observed, with ordered magnetic moments on the 4f and 5d electrons induced by the interaction with Fe. Increasing the Si content reduces the strength of the hy-bridization between the 4f and conduction-band states which is reflected in a growing occupation and magnetic polarization of the 4f states. Variations of the shape and intensity of the L2,3-edge dichroism spectra, discussed in a simple phenomenological model, show the importance of the exchange interaction between the Ce-4f and 5d electrons, spin polarized by the interaction with Fe at the interfaces, for the electronic structure of Ce at high Si concentration and low temperature. A model of the band structure of rare-earth transition-metal compounds permits to argue that magnetic order on the Ce 4f electrons in the multilayers is due to different mechanisms: to hybridization of the Ce-4f with the Fe-3d states at low Si concentration and to intra-atomic 4f-5d exchange at high Si concentration. This is at variance with magnetic order in the intermetallics CeSi2-delta and CeSi which results from interaction between the localized 4f magnetic moments mediated by the Si-derived (s,p) conduction electrons, in competition with the Kondo effect.