Multiferroic phases ofEu1−xYxMnO3

Abstract

We report on structural, magnetic, dielectric, and thermodynamic properties of Eu 1−x Y x MnO 3 for Y doping levels 0 ഛ x Ͻ 1. This system resembles the multiferroic perovskite manganites RMnO 3 ͑with R = Gd, Dy, Tb͒ but without the interference of magnetic contributions of the 4f ions. In addition, it offers the possibility to continuously tune the influence of the A-site ionic radii. For small concentrations x ഛ 0.1 we find a canted antiferromagnetic and paraelectric ground state. For higher concentrations x ജ 0.3 ferroelectric polarization coexists with the features of a presumably spiral magnetic phase analogous to the observations in TbMnO 3 . In the intermediate concentration range around x Ϸ 0.2 a multiferroic scenario is realized combining weak ferroelectricity and weak ferromagnetism, presumably due to a conelike magnetic structure.

Landau model for the phase diagrams of the orthorhombic rare-earth manganitesRMnO3(R=Eu, Gd, Tb, Dy, Ho)

“…For x=0.2 the canted ferromagnetism (M//y) characteristic of the A-AFM co-exists, at low temperatures, with the P//z polarization. 14 This co-existence may signal either the stabilization of a more complex magnetic phase 14 or a co-existence of both phases. Although there is no direct experimental evidence, the P//z phase is attributed to the stabilization of the Cycl-XZ phase, 52 as observed in GdMnO 3 under a magnetic field.…”

“…In the composition range 0<x<0.5, the (x-T) diagram of the solid solution has been investigated by different groups. 14,52,54 The temperature range of stability of the L-INC phase increases from 51K>T>46K at x=0 to 45K>T>22K at x=0.5. For x<0.2, the A-AFM phase is stabilized at low temperatures, although within a temperature band that rapidly narrows as x decreases.…”

“…This geometric effect can be controlled either in a stepwise manner, by using rare-earth elements with different ionic radius (from R=La 3+ to Pr 3+ , Eu 3+ , Gd 3+ , Tb 3+ , Dy 3+ , Ho 3+ , Yb 3+ and Lu 3+ ), or quasicontinuously, by tuning the average rare-earth radius in solid solutions in which the R 3+ ion is partially replaced by one isoelectric ion with different ionic radius, as in the case of the Eu 1-x Y x MnO 3 mixed system. [52][53][54][55] In the following we will analyze these two cases within the scope of the model presented above, as illustrative examples.…”

“…In this class of systems, external magnetic fields or chemical pressure fields originated from the partial substitution of a molecular unit, are capable of rotating or stabilizeing an electrical polarization. [11][12][13][14][15][16][17] Although these effects might mimic single phase effects like ferromagnetoelectricity (the linear magneto-electric effect) or piezoelectricity, they result from rather different mechanisms. Here, the magnetic or the stress fields induce magnetic phase transitions which, in turn, alter the symmetry of the system and modify the set of compatible secondary order parameters.…”

Magnetoimpedance spectroscopy of epitaxial multiferroic thin films

“…A short introduction into the basic principles of dielectric spectroscopy is given in the supplementary material part I. 29 MEC effects have been reported in a large range of materials by using dielectric spectroscopy, [30][31][32][33][34][35][36][37][38][39] where MEC effects were postulated in case that one of the following two criteria was fulfilled:…”