Dresden 2011 – scientific programme

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MA: Fachverband Magnetismus

MA 46: Magnetic Thin Films II

MA 46.4: Talk

Wednesday, March 16, 2011, 17:45–18:00, CHE 184

Anisotropic Paramagnetic Response Of CePt₅ Surface Alloys Studied With XMCD — •Christian Praetorius, Annemarie Köhl, Sebastian Götz, and Kai Fauth — Physikalisches Institut, Universität Würzburg, Am Hubland, 97074 Würzburg

We have investigated the magnetic response of structurally ordered CePt₅ surface alloys with X-ray Magnetic Circular Dichroism. Ultrathin CePt films were prepared on Pt(111) by evaporation of Cerium onto the clean surface and subsequent annealing. Depending on the initial Ce coverage these systems order in a variety of hexagonal phases which can be monitored by LEED, as shown in previous studies. Using Ce M_4,5-XMCD at normal and grazing incidence, respectively, we observe a strong anisotropy in the paramagnetic response which can be rationalized by consideration of the hexagonal crystal field. Likewise, the temperature dependence of the paramagnetic susceptibility is strongly influenced by the crystal field splitting of the Ce 4f¹ configuration. Our measurements provide access to the relevant energy scales in these surface alloys, which prove to deviate from those known from bulk CePt₅. The observed behavior at the lowest accessible temperatures (12 K) is indicative of a ferromagnetic instability around 7 K. Again, this finding contrasts the behavior of bulk CePt₅, known to order antiferromagnetically at low temperature.