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TT: Fachverband Tiefe Temperaturen

TT 44: Poster Session Correlated Electrons

TT 44.28: Poster

Donnerstag, 17. März 2011, 10:00–13:00, P1

³¹ P NMR study on Eu(Ni_1−xFe_x)₂P₂: from valence fluctuations to ferromagnetic order — •Michael Baenitz¹, Ramesh Nath², Rajib Sarkar¹, Hirale Jeevan³, Philipp Gegenwart³, Zarkir Hossain⁴, Nubia Caroca-Canales¹, Christoph Geibel¹, and Frank Steglich¹ — ¹MPI-CPfS , 01187 Dresden, Germany. — ²IISER-TVM, Trivandrum-695016, India. — ³1. Phys. Institut, Georg-August-Universität Göttingen, 37077 Göttingen, Germany. — ⁴Dept. of Physics, Indian Institute of Technology, Kanpur 208016 India.

Among unstable f shell sytems the magnetic phase diagram of Eu systems differs from that of Ce, Yb or U systems. In contrast to these systems the Eu valence mostly could not be tuned (by substitutions or external pressure) continuously between the magnetic (Eu⁺², J=7/2) and the non magnetic (Eu⁺³, J=0) state. Instead of that, first order valence transitions (like in EuNi₂(Si/Ge)₂) or an unstable, fluctuating valence (VF) at high temperatures (like in EuCu₂Si₂) are rather common. For EuCu₂Si₂ we have shown that upon Ge substitution the VF are suppressed and a small Kondo regime exist in the phase diagram before entering the antiferromagnetic ordered state on the Ge rich side. For the valence fluctuator EuNi₂P₂ the question arises whether a Kondo regime exists upon Fe substitution. In contrast to the EuCu₂(Si/Ge)₂ series the end point of the study here, EuFe₂P₂, is ferromagnetically ordered. This brings up the question of competition and/or coexistence of ferromagnetic and Kondo type of interactions in this new series. ³¹ P NMR measurements are carried out on Eu(Ni_1−xFe_x)₂P₂ samples with x = 0, 0.15, 0.5 and 1.