Exploiting interfacial and size effects to construct oxide superlattices with robust and tunable magnetoelectric properties at room temperature

Abstract

We propose a strategy to create materials displaying robust and tunable magnetoelectric multiferroic properties at room temperature. The key idea is to construct heterostructures that combine two different constituents: (1) Compound BiFeO3, which presents strong ferroelectric and antiferromagnetic orders well above room temperature, but displays a small magnetic moment. (2) A ferromagnetic insulator (e.g., BiMnO3) that is only required to couple magnetically with BiFeO3. Our simulations show that it is possible to combine such materials to create superlattices that present (i) a room-temperature multiferroic state with relatively large magnetization (up to 0.3 µB per transition metal atom, with the possibility to improve by finding a suitable replacement for BiMnO3), (ii) an amply customizable magnetic behavior, and (iii) a strong magnetoelectric coupling. Thus, the new design strategy successfully addresses the greatest challenge in the area of magnetoelectric multiferroics, exploiting interfacial couplings and size (layer-thickness) effects to produce materials apt for applications.

Ferroelectricity and Ferromagnetism Achieved via Adjusting Dimensionality in BiFeO3/BiMnO3 Superlattices

“…Hence, it is worth considering the combination of BFO and BMO with both intriguing ferroelectric and magnetic states in a superlattice system. In parallel, a nanoscale checkerboard structure and a (111)-oriented superlattice structure had been proposed theoretically in the BFO/BMO system with enhanced magnetoelectric properties. , However, due to extremely harsh growth conditions of BMO films, synthesizing pure-phase BFO/BMO SLs with sharp interfaces experimentally remains a challenge. , Here, we report the realization of high-quality (BFO n /BMO 10 ) 4 ( n = 1, 2, 5, 8, and 10, the dimensionality of BFO layers per period) on (001)-oriented SrTiO 3 (STO) substrates with considerable ferroelectric polarizations and tunable magnetic moments. We observe decent ferroelectricity in SLs, even as the dimensionality of BFO layers per period is reduced to about five-unit cells when keeping the BMO layers the same.…”

“…7−13 Moreover, the potential coupling of spontaneous polarization and magnetic moment at the interfaces of ferroelectric layers and FM layers in such a superlattice system tends to be fascinating. 14,15 As the robust RT multiferroics, BiFeO 3 (BFO) is actually AFM, which limits its applications. 16−18 Among the other most promising materials, it is worth noting that BiMnO 3 (BMO) exhibits a magnetic moment of about 3.6 μB/Mn with a FM transition temperature T C of about 105 K. 19,20 Interestingly, epitaxial BMO films sometimes are believed to be weak ferroelectricity, although its paraelectric character in bulk with the C2/c space group is accepted.…”

“…In parallel, a nanoscale checkerboard structure and a (111)-oriented superlattice structure had been proposed theoretically in the BFO/BMO system with enhanced magnetoelectric properties. 14,15 However, due to extremely harsh growth conditions of BMO films, synthesizing pure-phase BFO/BMO SLs with sharp interfaces experimentally remains a challenge. 26,27 Here, we report the realization of high-quality (BFO n /BMO 10 ) 4 (n = 1, 2, 5, 8, and 10, the dimensionality of BFO layers per period) on (001)-oriented SrTiO 3 (STO) substrates with considerable ferroelectric polarizations and tunable magnetic moments.…”

“…Recently, multiferroic materials exhibit a wide range of potential applications in multifunctional devices, such as memory devices, , sensors, , and so forth. However, regarding all the important ABO 3 perovskite oxide families, a single-phase material that presents strong polarization and magnetization simultaneously at room temperature (RT) is rare. , Fortunately, artificial oxide superlattices (SLs) present intriguing opportunities for integrating multifunction in a system, especially in ferroelectricity and ferromagnetism. − Moreover, the potential coupling of spontaneous polarization and magnetic moment at the interfaces of ferroelectric layers and FM layers in such a superlattice system tends to be fascinating. , As the robust RT multiferroics, BiFeO 3 (BFO) is actually AFM, which limits its applications. − Among the other most promising materials, it is worth noting that BiMnO 3 (BMO) exhibits a magnetic moment of about 3.6 μB/Mn with a FM transition temperature T C of about 105 K. , Interestingly, epitaxial BMO films sometimes are believed to be weak ferroelectricity, although its paraelectric character in bulk with the C 2/ c space group is accepted. − …”