Realization of Large Electric Polarization and Strong Magnetoelectric Coupling in BiMn₃Cr₄O₁₂

Abstract

Magnetoelectric multiferroics have received much attention in the past decade due to their interesting physics and promising multifunctional performance. For practical applications, simultaneous large ferroelectric polarization and strong magnetoelectric coupling are preferred. However, these two properties have not been found to be compatible in the single-phase multiferroic materials discovered as yet. Here, it is shown that superior multiferroic properties exist in the A-site ordered perovskite BiMn Cr O synthesized under high-pressure and high-temperature conditions. The compound experiences a ferroelectric phase transition ascribed to the 6s lone-pair effects of Bi at around 135 K, and a long-range antiferromagnetic order related to the Cr spins around 125 K, leading to the presence of a type-I multiferroic phase with huge electric polarization. On further cooling to 48 K, a type-II multiferroic phase induced by the special spin structure composed of both Mn- and Cr-sublattices emerges, accompanied by considerable magnetoelectric coupling. BiMn Cr O thus provides a rare example of joint multiferroicity, where two different types of multiferroic phases develop subsequently so that both large polarization and significant magnetoelectric effect are achieved in a single-phase multiferroic material.

Ferroelectricity driven by soft phonon and spin order in multiferroic BiMn3Cr4O12

“…The crystal structure of BMCO with cubic symmetry is shown in Figure A. For this specific A ‐site ordered perovskite with the general chemical formula of ( AA ′ 3 ) B 4 O 12 , the A ′‐sites are occupied by Mn ions with square coordinated MnO 4 units while the CrO 6 octahedra are remarkably tilted . At temperatures higher than T FE1 , the paraelectric BMCO is a paramagnetic (PM) insulator.…”

“…The second puzzle concerns the large spin‐induced ferroelectric polarization (0.19 μC/cm 2 ) in the BMCO ceramic sample, which is more than two orders of magnitude larger than that in polycrystalline LMCO (0.15 × 10 −2 μC/cm 2 ) . This is remarkable, considering that both BMCO and LMCO exhibit not only the isostructural cubic symmetry at high temperature but also the same collinear G ‐type AFM order composed of Mn and Cr sublattices at low temperature . According to Ref.…”

“…Such a novel multiferroicity can be described by the so‐called anisotropic symmetric exchange mechanism . Subsequently, a joint multiferroic material showing coexistence of both type‐I and type‐II multiferroicity was realized in single‐phase BiMn 3 Cr 4 O 12 (BMCO) perovskite . Starting from the high‐temperature cubic space group (No.…”

“…On further decreasing the temperature to T N2 ≈ 48 K, another similar collinear G ‐type AFM transition occurs for the A ′‐site Mn sublattice. It is the interaction between these two magnetic sublattices that leads BMCO into the type‐II multiferroic state (FE2 phase), which is characterized by the second ferroelectric transition temperature T FE2 = T N2 and the considerable magnetoelectric coupling . In addition, it is important to note that this spin‐induced ferroelectric polarization in the BMCO ceramic sample can reach a value of 0.19 μC/cm 2 at zero magnetic field .…”

“…It is the interaction between these two magnetic sublattices that leads BMCO into the type‐II multiferroic state (FE2 phase), which is characterized by the second ferroelectric transition temperature T FE2 = T N2 and the considerable magnetoelectric coupling . In addition, it is important to note that this spin‐induced ferroelectric polarization in the BMCO ceramic sample can reach a value of 0.19 μC/cm 2 at zero magnetic field . Due to both the considerable ferroelectric polarization and the remarkable magnetoelectric coupling, BMCO can therefore be regarded as an uncommon example of joint multiferroics, in which two distinct types of multiferroic phases emerge subsequently.…”