A novel perovskite oxide chemically designed to show multiferroic phase boundary with room-temperature magnetoelectricity

Abstract

There is a growing activity in the search of novel single-phase multiferroics that could finally provide distinctive magnetoelectric responses at room temperature, for they would enable a range of potentially disruptive technologies, making use of the ability of controlling polarization with a magnetic field or magnetism with an electric one (for example, voltage-tunable spintronic devices, uncooled magnetic sensors and the long-searched magnetoelectric memory). A very promising novel material concept could be to make use of phase-change phenomena at structural instabilities of a multiferroic state. Indeed, large phase-change magnetoelectric response has been anticipated by a first-principles investigation of the perovskite BiFeO3–BiCoO3 solid solution, specifically at its morphotropic phase boundary between multiferroic polymorphs of rhombohedral and tetragonal symmetries. Here, we report a novel perovskite oxide that belongs to the BiFeO3–BiMnO3–PbTiO3 ternary system, chemically designed to present such multiferroic phase boundary with enhanced ferroelectricity and canted ferromagnetism, which shows distinctive room-temperature magnetoelectric responses.

The Polar/Antipolar Phase Boundary of BiMnO3–BiFeO3–PbTiO3: Interplay among Crystal Structure, Point Defects, and Multiferroism

“…Results for the binary‐ and ternary‐system compositions are shown in Figure a. Both samples presented Arrhenius‐type behavior with similar room‐temperature resistivity below 10 6 Ω cm, which are not high enough to withstand the high electric fields required for ferroelectric characterization (resistivity values of bulk ferroelectric materials typically exceeds 10 9 Ω cm and even reaches up to 10 12 Ω cm) . Besides, a single mechanism seems to dominate the total σ along the whole temperature range, with activation energy of 0.4–0.45 eV.…”

“…It can lead to the appearance of morphotropic phase boundaries (MPBs) at which property enhancement takes place and phase‐change functional responses can be obtained . Indeed, the occurrence of phase‐change magnetoelectric phenomena has been experimentally demonstrated for specific compositions of the BiFeO 3 –BiMnO 3 –PbTiO 3 ternary system placed at MPBs between polymorphs of monoclinic Cc and tetragonal P 4 mm symmetries . The underlying mechanism is the discrete rotation of the magnetization due to an electric field induced transformation between the ferroelectric (multiferroic) polymorphs.…”

Delicate Balance among Three Ferroic Polymorphic Phases in BiFeO3–BiMnO3–PbTiO3

“…23 Room-temperature magnetoelectricity is obtained, not only due to an electric field driven phase-change between the two multiferroic polymorphs, but also by the presence of a transverse lattice softening within the monoclinic phase that gives rise to linear magnetoelectric effect. 22 The latter phenomenology would be analogous to that described in high-sensitivity MPB ferroelectrics, which is responsible for the very-high piezoelectric responses. 24 Indeed, a theoretical study has pointed out to the possibility of obtaining enhanced magnetoelectric responses at multiferroic analogues associated with this lattice transverse softening.…”

“…Indeed, a controversy persists regarding the actual existence of the Cc polymorph in the BiFeO3-PbTiO3 binary system. 10,22,28 However, the presence of transverse lattice softening and a magnetic SRO transition, 14,23 both phenomena characteristic of the monoclinic symmetry, seems to confirm the presence of the Cc phase in the ternary system. Additionally, the symmetry of the pseudo-cubic polymorph that resulted from slow cooling of composition 2 was also investigated.…”

“…21 We have recently reported the occurrence of phase-change magnetoelectric phenomena for a specific composition of the BiFeO3-BiMnO3-PbTiO3 ternary system, for which coexistence of phases with monoclinic Cc and tetragonal P4mm symmetries was found. 22 In this material, both polymorphs are ferroelectric and antiferromagnetic (AFM), yet a weak ferromagnetic component appears within the Cc phase, as a result of a spin reorientation (SRO) transition within its AFM state. 23 Room-temperature magnetoelectricity is obtained, not only due to an electric field driven phase-change between the two multiferroic polymorphs, but also by the presence of a transverse lattice softening within the monoclinic phase that gives rise to linear magnetoelectric effect.…”