Multiferroics and Magnetoelectrics: A Comparison between Some Chromites and Cobaltites

Abstract

Oxides containing magnetic 3d transition metals offer a large family of structures with frustrated magnetic networks. Some of those incommensurate antiferromagnetic structures are responsible for the local breaking of inversion symmetry so that these oxides are called spin-induced ferroelectrics. As listed in the introduction of this short review, the number of these multiferroics continues to increase. As for applications, the coupling between these ferroisms is needed; some magnetic oxides, despite a lack of ferroelectric ground state, exhibit large magnetoelectric coupling with a magnetic-field-induced polarization. Thus, they are classified as “magnetoelectrics”. In the present review, we focus on recently studied systems showing ferroelectric-like behaviors or large magnetoelectric coefficients. This will be illustrated by chromites with the comparison between ceramics of CuCrO2 and AgCrS2: they exhibit different antiferromagnetic ground states, centrosymmetric and noncentrosymmetric. For the magnetoelectrics, the example of the cobaltite, CaBaCo4O7, which is a polar ferrimagnet, is taken to illustrate the existence of large magnetoelectric coefficients in crystals. Then, the existence of spin-induced ferroelectricity in centrosymmetric orthochromites (RECrO3 with RE = Lu or Er) is discussed. Through this selection of potential multiferroics or magnetoelectrics, it is clear that many magnetic materials in different forms (bulk/crystal/thin film) remain to be studied.

Multiglass properties and magnetoelectric coupling in the uniaxial anisotropic spin-cluster-glassFe2TiO5

“…Rev. B 90, 144426 (2014) 4 are found to be consistent with the earlier report [21]. On the basis of absence of (112) peak intensity in the powder neutron diffraction data, Atzmony et al [11] Therefore, in the case of partial disorder, one can observe (112) peak with some finite intensity even in the XRD pattern.…”

Multiferroicity and magnetoelectric coupling enhanced large magnetocaloric effect in DyFe0.5Cr0.5O3

“…4 However, the origin of multiferroicity in these orthochromites is still under debate. 5 In the case of DyFe 0.5 Cr 0.5 O 3 , the influence of the magnetic interaction, such as Dy-O-(Fe/Cr), on the FE polarization as well as the spin-phonon coupling in the vicinity of the magnetic transitions as discussed below strongly indicate that the magnetic interaction between the magnetic ions plays an important role in the appearance of ferroelectricity in this compound.…”

“…And even some contrary results were reported by different groups. 3,5 On the other hand, it was recently proposed that magnetocaloric effects (MCE) can be enhanced by the ME coupling in multiferroics. 6 In fact, giant MCE has been observed near the magnetic phase transitions in rare-earth chromites and multiferroic manganites.…”

Atypical multiferroicity of HoCrO3 in bulk and film geometry

“…1 Specially, the concomitant emergence of ferroelectric (FE) and (anti)ferromagnetic order in a chemically single-phase material and strong coupling between these two, termed magnetoelectric coupling, is extremely promising for the future generation of memory devices. [4][5][6][7][8][9][10] Hopefully, the results of RCrO 3 (R = Lu, Sm, Er, and Gd) clearly demonstrate a significantly large magnitude (BmC cm À2 ) of electric polarization (P) at reasonably high temperature, [11][12][13] which is attractive for technological applications. The current focus mainly involves searching for new materials which have multiferroic order close to room temperature with significant spontaneous polarization.…”