Neutron powder diffraction study on Nd2BaCuO5 oxide

Abstract

The magnetic behaviour of Nd 2 BaCuO 5 oxide has been studied by means of neutron powder diffraction at low temperatures. This oxide behaves as antiferromagnetic with a Néel temperature of 7.8 K, and the magnetic structure can be described on the basis of a propagation vector k = [0, 0, 1/2]. The Cu 2+ magnetic moments are aligned along the c-axis of the crystal structure, while the Nd 3+ magnetic moments lie in the ab-plane. The experimental values of the ordered moments at 1.7 K are 0.84 (8) and 0.78 (4)µ B for copper and neodymium ions, respectively.

Magnetic characterization of Pr2BaCuO5

“…Thus, the best agreement between the experimental and calculated neutron diffraction patterns has been reached considering the antiferromagnetic Pr 3+ magnetic moments (m Pr ) coupled in the ab-plane of the structure with a small component along the c-axis, and the Cu 2+ magnetic moments (m Cu ) antiferromagnetic aligned along the c-axis of the structure, as depicted in figure 7. It is worth noting that this non-collinear antiferromagnetic structure does not change from 2 to 15 K. A similar magnetic structure has been reported for Nd 2 BaCuO 5 oxide [23], but a propagation vector k = [0, 0, 1/2] has been used to index the magnetic contribution to the diffraction patterns. The differences found in the magnetic structures could be attributed to the different anisotropy of the Pr 3+ and Nd 3+ ions.…”

“…A detailed mechanism through the magnetic interactions that take place in these P4/mbm-R 2 BaCuO 5 oxides has already been given [15,23] and it was established that the magnetic ordering is mainly governed by the effective orbital overlap of Cu-O-R superexchange interactions, where the half-filled d x 2 −y 2 orbital of Cu 2+ is involved. This proposed pathway justifies the change of the sign of interactions from ferromagnetism in the La 2 BaCuO 5 oxide to antiferromagnetism in the isostructural Pr 2 BaCuO 5 and Nd 2 BaCuO 5 oxides, where both Cu 2+ and R 3+ paramagnetic sublattices are involved in the superexchange interactions.…”

High-temperature ferroelectric order and magnetoelectric coupling driven by the magnetic field cooling effect in R2BaCuO5(R=Er,Dy,Sm)<

“…Neutron diffraction studies have been performed for Nd and Gd compounds at the R site. The magnetic structure of Nd 2 BaCuO 5 was suggested on the basis of a propagation vector k = [0, 0, 1/2] below the Néel temperature of 7.8 K, where the Cu 2+ and Nd 3+ magnetic moments were aligned along the crystallographic c axis and in the ab plane, respectively [23]. Recent neutron results on isotopically substituted 160 Gd 2 BaCuO 5 proposed an incommensurate magnetic structure with a propagation vector k = [0, 0, 1/2 − δ] below 12 K, followed by a commensurate structure with a k = [0, 0, 1/2] propagation vector at 5 K, which was accompanied with a Gd spin reorientation and a magnetostructural transition [24].…”

High-temperature ferroelectric order and magnetic field-cooled effect driven magnetoelectric coupling in R2BaCuO5 (R= Er, Dy, Sm)

“…The magnetic structure of Nd 2 BaCuO 5 was suggested on the basis of a propagation vector k = [0, 0, 1/2] below the Néel temperature of 7.8 K, where the Cu 2+ and Nd 3+ magnetic moments were aligned along the crystallographic c-axis and in the ab-plane, respectively. 24 Recent neutron results on isotopically substituted 160 Gd 2 BaCuO 5 proposed an incommensurate magnetic structure with a propagation vector k = [0 0 1/2 -δ] below 12 K, followed by a commensurate structure with a k = [0 0 1/2] propagation vector at 5 K, which was accompanied with a Gd spin re-orientation and a magnetostructural transition. 25 The considerable magnetic refrigeration with a maximum magnetic entropy change of -∆S M ≈ 10.4 J/kg K at Néel temperature and refrigerant capacity of ≈ 263 J/kg were suggested for and R 2 BaCoO 5 33 attract special attentions for the multiferroic order, proposing different origins behind the occurrence of ferroelectric order.…”