Valence Instability and Magnetic Polarization of Ce Atoms near the Interface of Ce/Fe Multilayers Studied by Magnetic Ci
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Valence Instability and Magnetic Polarization of Ce Atoms near the Interface of Ce/Fe Multilayers Studied by Magnetic Circular X-Ray Dichroism.
F. KLOSE*, S. PIZZINI**, C. GIORGETFI**, 0. SCHULTE**, F. BAUDELET**, E. DARTYGE**, G. KRILL**,W. FELSCH* and A.FONTAINE** *I. Physikalisches Institut, Universitat Gottingen, Bunsenstr. 9. 3400 Gottingen, Germany **LURE. Batiment 209D, Universit6 Paris-Sud, 91405 Orsay, France
ABSTRACT An experimental study of conventional x-ray absorption and of magnetic circular x-ray dichroism has been performed on Ce/Fe multilayers at the Ce L 2 ,3 and the Fe-K edge, to characterize the impact of the interaction of Ce and Fe on the local electronic and magnetic structure of the interface. The spectra reveal that the interaction has two effects. First, on a depth scale of up to 15 A near the interface, the Ce atoms adopt the electronic structure of the oa-phase, with itinerant 4f states. Second, a large portion ( =10 A) of these aX-like Ce atoms is magnetically polarized and carries an ordered magnetic 5d moment. The Fe-3d and Ce-Sd moments are antiferromagnetically coupled. Interface mixing on a length scale of the magnetic polarization can be excluded.
INTRODUCTION During the last years, the synthesis and study of thin layer and multilayer structures composed of different metals have attracted considerable interest. This is because the properties of such artificial materials can be significantly different from those of any of the components. The present paper deals with multilayers prepared of cerium and iron. The stacking of a rare earth and a transition metal is particularly attractive in view of the resulting magnetic properties, as more localized 4f and itinerant d electronic states are combined. Consequences originating from the interaction of such states are immediately evident in intermetallic compounds. In CeFe2 for example, a compound well known for its peculiar properties, which is of particular interest in the present context, delocalization of the Ce-4f states and quenching of their orbital moment due to a strong hybridization with the Fe-3d states results in ferromagnetic order with an unusually low Curie temperature (=230 K), a small magnetic moment of the Fe ions (=1.4 JtB) and a magnetic moment of the Ce ions (--0.5 91B) coupled antiferromagnetically to the Fe moment[ 1]. It has been shown recently that the saturation magnetization of Ce/Fe multilayers at room temperature is considerably reduced as compared to bulk Fe[2]. This addresses the problem of the interaction of Ce and Fe at the interface of these multilayers. It is the aim of this work to provide a microscopic characterization of the electronic and magnetic structure at the Ce-Fe interface. This information is derived by absorption spectroscopy at the L2,3 edges of Ce and the K edge of Fe with circularly polarized hard x-rays, taking benefit from the atomic selectivity of the method and the appearance of magnetic dichroism near the absorption edges involved.
MAGNETIC CIRCULAR X-RAY DICHROISM Conventional x-
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