Universität zu Köln

Heyer, O., Link, P., Wandner, D., Ruschewitz, U. and Lorenz, T. (2011). Thermodynamic properties and resistivity of the ferromagnetic semiconductor EuC2. New J. Phys., 13. BRISTOL: IOP PUBLISHING LTD. ISSN 1367-2630

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Abstract

EuC2 is a ferromagnet with a Curie temperature of T-C similar or equal to 15 K. It is semiconducting with the particularity that the resistivity drops by about five orders of magnitude on cooling through T-C, which is therefore called a metal-insulator transition. In this paper, we study the magnetization, specific heat, thermal expansion and the resistivity around this ferromagnetic transition on high-quality EuC2 samples. At T-C we observe well-defined anomalies in the specific heat c(p)(T) and thermal expansion alpha(T) data. The magnetic contributions of c(p)(T) and alpha(T) can satisfactorily be described within a mean-field theory, taking into account the magnetization data. In zero magnetic field, the magnetic contributions of the specific heat and thermal expansion fulfil a Gruneisen scaling, which is not preserved in finite fields. From an estimation of the pressure dependence of T-C via Ehrenfest's relation, we expect a considerable increase of T-C under applied pressure due to a strong spin-lattice coupling. Furthermore, the influence of weak off-stoichiometries delta in EuC2 +/-delta was studied. It is found that delta strongly affects the resistivity, but hardly changes the transition temperature. In all these aspects, the behaviour of EuC2 strongly resembles that of EuO.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Heyer, O. UNSPECIFIED UNSPECIFIED UNSPECIFIED Link, P. UNSPECIFIED UNSPECIFIED UNSPECIFIED Wandner, D. UNSPECIFIED UNSPECIFIED UNSPECIFIED Ruschewitz, U. UNSPECIFIED UNSPECIFIED UNSPECIFIED Lorenz, T. UNSPECIFIED UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-485094
DOI:	10.1088/1367-2630/13/11/113041
Journal or Publication Title:	New J. Phys.
Volume:	13
Date:	2011
Publisher:	IOP PUBLISHING LTD
Place of Publication:	BRISTOL
ISSN:	1367-2630
Language:	English
Faculty:	Unspecified
Divisions:	Unspecified
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language RARE-EARTH DICARBIDES; THERMAL-EXPANSION; EUROPIUM OXIDE; TRANSITION; FIELDS; PHASE; KOE; EUO Multiple languages Physics, Multidisciplinary Multiple languages
URI:	http://kups.ub.uni-koeln.de/id/eprint/48509