Measurements of thermodynamic and transport properties of EuC${}_2$: a low-temperature analogue of EuO

Abstract

EuC${}_2$ is a ferromagnet with a Curie-temperature of $T_C\simeq 15$K. It is semiconducting with the particularity that the resistivity drops by about 5 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 EuC${}_2$ 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 fulfill a Grüneisen-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 EuC${}_{2\pm \delta }$ was studied. It is found that $\delta$ strongly affects the resistivity, but hardly changes the transition temperature. In all these aspects, the behavior of EuC${}_2$ strongly resembles that of EuO.

7 pages, 6 figures

References in corpus (2)

• Metal-insulator transition in EuO
• Thermodynamics of the coupled spin-dimer system TlCuCl3 close to a quantum phase transition

Cited by in corpus (2)

• Lattice strain accompanying the colossal magnetoresistance effect in EuB${}_6$
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