Enhancement of magnetoelectric effect by combining different interfacial coupling mechanisms

Abstract

First-principles calculations were used to investigate the interfacial electronic structure and magnetoelectric effect in the Fe/PbTiO3 heterointerface. We demonstrate that the large magnetoelectric effect in this system is determined by the combination of different magnetoelectric coupling mechanisms, i.e., the conjunction of interface bonding mechanism and the electrostatic screening of the spin-polarized carriers. The change of induced magnetic moments on interfacial Ti atoms is due to the variation of interface bonding when the ferroelectric polarization reverses, while the contribution to magnetoelectric coupling from interfacial Fe atoms is determined by the electrostatic screening of spin-polarized carriers. The combination of different interfacial magnetoelectric coupling mechanisms enhances the magnetoelectric coefficient at the Fe/PbTiO3 heterointerface to be several times larger in magnitude than that of individual magnetoelectric coupling mechanism. Our results indicate a new strategy to design multiferroic materials with large magnetoelectric effects.

Giant magnetoelectric effect at the graphone/ferroelectric interface

“…PbTiO 3 has a larger out-of-plane polarization and a smaller ferroelectric critical size than common ferroic materials such as BaTiO 3 and BiFeO 3 49 – 51 . In addition, the MEC of PbTiO 3 -based heterostructures is larger than that of BaTiO 3 system 52 . Therefore, PbTiO 3 is selected as the ferroelectric layer in the present study.…”

Artificial multiferroic heterostructures

“…For instance, density functional theory (DFT) calculations for Fe/BaTiO 3 (001) show a large surface magnetoelectric response whose origin is largely attributed to changes in the chemical bonding at the interface, i.e., to modulations in the Ti 3d, Fe 3d and O 2p orbital overlap upon reversal of the ferroelectric polarization direction due to the displacement of the Ti atoms, which additionally become magnetically polarised. [105][106][107][108][109][110] The latter effect has been observed experimentally in Fe/BaTiO 3 (001) by so X-ray resonant magnetic scattering, 111 which shows that the Ti cations become ferromagnetic by proximity with the Fe lm, turning the interface region of BaTiO 3 both ferroelectric and ferromagnetic, i.e., multiferroic, at room temperature. The modulation of the charge carrier density at the interface can also modify strongly the surface magnetic anisotropy of a ferromagnetic material via spin-orbit coupling through a change in the relative electron occupancy of the different d orbitals.…”

Spin-dependent resonant tunneling of multiferroic tunnel junction via head-to-head 180° domain wall

“…On the other hand, the interface bonding causes charge redistribution between the majority and minority spins for Ti 3d and O 2p states, giving rise to induced magnetic moments on the interfacial Ti and O atoms of about À0.04 and 0.04, respectively. Previous first-principles calculations 40 have demonstrated that large magnetoelectric coupling occurs in the Fe/PbTiO 3 heterointerface due to combination of different magnetoelectric coupling mechanisms when the ferroelectric polarization of PbTiO 3 reverses. Second, it is clear that the occupancies of Ti d xz þ d yz states are increased observably as the TiO 2 atomic plane moves from the interfacial to the central layer while the occupancy of Ti d xy states in the central TiO 2 layer is much less than that in the TiO 2 monolayers with l ¼ À4 and À2.…”

“…The work of separation between Fe and PbTiO 3 slabs is determined to be 2.62 J/m 2 , which is more than four times larger than the Fe/BaTiO 3 system. 40 domain wall. As we see later, the screening electronic charges are situated on the Ti 3d orbitals, so it is more meaningful to take into account the planar-averaged electrostatic potentials of the TiO 2 atomic planes.…”

“…This feature is associated with the interface bonding between the O 2p and the Fe 3d orbitals, which displays a large exchange splitting and results in the induced antiparallel magnetic moment on the interfacial Ti 3d orbitals. 27,40,43 Except for the central TiO 2 layer, the asymptotical behavior of the majority-spin electrons shows an exponential-like decay and can be fitted satisfied by the Airy-like function as nðzÞ ¼ p 1 z À1=4 expðÀp 2 z 3=2 Þ, 44 where p 1 and p 2 are the fitting parameters. Including the central layer, the whole curve of the majority-spin electrons can also be fitted quite well by the function of nðzÞ ¼ p 1 expðÀp 2 jzj 3=2 Þ.…”