Magnetic phase transition in two-phase multiferroics predicted from first principles

Magnetoelectric coupling at metal surfaces

“…In typical ferroelectric materials like the perovskites, the mechanisms leading to ferroelectricity and ferromagnetism even seem to exclude each other: a stable electric polarization arises only in the case of empty d-shells of the transition-metal ions, while partially filled d-shells are responsible for the ferromagnetism [33]. A second group are composite materials in which ferroelectric and ferromagnetic phases are brought into close contact so that electric and magnetic dipoles couple via the interface, driven by elastic [5,34] or electronic effects [8,7]. Especially in laminated multilayer compounds, larger effects are found.…”

“…The microscopic processes that lead to MEC in single-phase compounds are rather complex and still lack a complete theoretical understanding. In a different approach, multiphase compounds are engineered with the ferroelectric and ferromagnetic phases in close contact so that electric and magnetic dipoles couple via the interface [7,8]. In both approaches, the electric field changes the electric polarization by displacing positive and negative ions with respect to each other.…”

Ferroelectric Field Effect Control of Magnetism in Multiferroic Heterostructures

“…For Fe/BaTiO 3 (001), the results of density functional theory (DFT) calculations predict a large surface magnetoelectric response whose origin is largely attributed to changes in the chemical bonding at the interface, in particular, to hybridization between the Ti 3d, Fe 3d and O 2p orbital states, which is found to change significantly upon reversal of the ferroelectric polarization direction due to the displacement of the Ti atoms. The magnetoelectric coupling coefficient for 2 ML Fe/BaTiO 3 is estimated to be α = 0.01 Oe cm V −1 Duan et al (2006) while for 1 ML Fe/PbTiO 3 , α = 0.073 Oe cm V −1 Fechner et al (2008); the effect of Fe oxidation has been predicted not to affect significantly the magnetoelectric coupling Fechner et al (2009). In Fe/MgO(001), a surface magnetoelectric coupling α s = 1.1 × 10 −13 Oe cm 2 V −1 is found, significantly larger by a factor of 3.8 than that of a free standing Fe layer Niranjan et al (2010); also in this system a linear change in the magnetocrystalline anisotropy with the applied electric field is reported.…”

“…In such instances, it is common to define an effective magnetoelectric constant corresponding to the change in magnetization for a given applied electric field (or conversely, the change in electric polarization for a given applied magnetic field). In composite systems relying on interfacial effects, it is useful to define a surface (interface) magnetoelectric coefficient α s , corresponding to the change in surface magnetization for a given applied electric field Duan et al (2008);Fechner et al (2008); Niranjan et al (2009). With the definition given above, the linear magnetoelectric constant has units of s m −1 in S.I.…”

Determination of surface and interface magnetic properties for the multiferroic heterostructure Co/BaTiO3using spleed and arpes

“…I the corresponding structure at the interface of the Co/BTO system is shown schematically. The crystal structure of the Co/BTO system shows many similarities when compared to the Fe/BTO system, which was investigated in previous studies [7,11,27]. The first Co layer (Co O ) is placed on top of the O atoms of the Ti-O terminated BTO surface.…”