Eur. Phys. J. B (2018) 91: 28
https://doi.org/10.1140/epjb/e2017-80604-7

Regular Article

Ferromagnetism and ferroelectricity in EuX (X = O, S): pressure effects

¹ Laboratoire de Physique Computationnelle des Matériaux, Université Djillali Liabés de Sidi Bel-Abbés, Sidi Bel-Abbés 22000, Algeria
² Département de Physique, Institut de Sciences de la nature et de vie & Sciences exactes (SNV-SE), Centre Universitaire Ahmed ZABANA, Relizane, Relizane 48000, Algeria
³ Laboratoire d’Elaboration et Caractérisation Physico Mécanique et Métallurgique des Matériaux (ECP3M), Département de Génie Electrique, Faculté des Sciences et de la Technologie, Université Abdel Hamid Ibn Badis de Mostaganem, Mostaganem 27000, Algeria

^a e-mail: kacimi200x@yahoo.fr

Received: 24 October 2017
Received in final form: 22 November 2017
Published online: 7 February 2018

Abstract

Ferromagnetism and ferroelectricity in Eu monochalcogenides have been investigated by ab initio density functional theory in the DFT+U approach. Exchange interaction parameters and Curie temperatures under pressure are studied and discussed using Heisenberg Hamiltonian with first and second-nearest-neighbor interactions. The calculations showed that the hydrostatic pressure perfectly improves the Curie temperature (EuO: T_C = 175 K; EuS: T_C = 33.8 K) and in the other hand it cannot induce the spontaneous polarization (P_s). The effect of uniaxial and biaxial pressure is also studied. Although the uniaxial strains slightly increases the Curie temperature, it ensures the ferrolectricity in these systems by producing a spontaneous polarization of the order of P_s(EuO) = 57.50 μC/cm² and P_s(EuS) = 42.86 μC/cm² with pressures of 5% and 4%, respectively. The search for new model systems is a necessity to better understand the physics related to multiferroïc materials and to consider possible applications.