Interface‐Coupled BiFeO₃/BiMnO₃ Superlattices with Magnetic Transition Temperature up to 410 K

Abstract

polarization is very small (0.1 µ C cm −2 at ≈90 K) or it is even paraelectric. [ 4 ] In BFO, strong FE behavior (Ferroelectric transition temperature, T C,FE ≈ 1103 K) coexists together with antiferromagnetism (AFM). BFO has an incommensurate cycloidally modulated G-type AFM structure with a large period of 62 nm (Néel temperature, T N ≈ 650 K). [ 5,6 ] Despite having ferroelectric and magnetic ordering at high temperatures, BFO has drawbacks for practical applications. Most notably the weak FM-like magnetic behavior results from destruction of its incommensurate magnetic structure leading to AFM. [ 6 ] With strong ferromagnetic behavior in BMO and strong ferroelectric behavior in BFO, various studies have suggested combining BMO and BFO in order to achieve room-temperature (RT) multiferroicity. [7][8][9][10] One approach is to modify the local spin confi guration of Fe by chemical doping at the B -site. [ 8,9 ] By 50% doping, this simple concept could result in ordered double perovskite ferrites of Bi 3+ 2 Fe6 (TM = transition metal: Cr, Mn, Co, Ni, and Cu) giving antiferromagnetically coupled high spin state of the TM and Fe. However, this concept has not been widely realized due to the lack of cation ordering as a result of negligible differences in ionic valences and ionic radii. [11][12][13][14][15] On the other hand, disordered double perovskites (notably BiFe 0.5 Mn 0.5 O 3 (BFMO) and Bi 2 CoMnO 6 (BCMO)) show a strongly enhanced T C albeit with lower magnetic moment than expected for the ordered structure. [ 16,17 ] Pálová et al. extended the idea of ordered double perovskites by theoretically studying BFMO with an ordered nanoscale checkerboard structure (NCB-BFO/BMO, see Figure 1 a), i.e., columnar B -site ordering. [ 10 ] Their calculations predict that an ordered NCB-BFO/BMO would be ferroelectric and ferrimagnetic (FiM) with M S of 3.8 µ B /Fe-Mn pair and T C of 406 K, as a result of magnetic ordering arising from the superexchange coupling between the neighboring AFM-Fe and FM-Mn. [ 10 ] Unfortunately, spontaneous columnar B -site ordering is not expected and high quality growth of artifi cial 1:1 BFO/BMO superlattices along the 〈110〉 direction is very hard.

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.…”

“…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. 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.…”

Epitaxial Growth of Aurivillius Bi3Fe2Mn2Ox Supercell Thin Films on Silicon

“…Among the known single-phase multiferroic materials, the BiFeO 3 (BFO) and BiMnO 3 (BMO) perovskite oxides are well explored systems. The BFO system presents ferroelectric properties with a high Curie temperature of 1103 K and weak antiferromagnetic properties, with a Néel temperature of 640 K . The BMO system, conversely, displays strong ferromagnetic properties with a Curie temperature of 105 K but lacks robust ferroelectricity, with a Curie temperature of 760 K .…”

“…The BFO system presents ferroelectric properties with a high Curie temperature of 1103 K and weak antiferromagnetic properties, with a Néel temperature of 640 K . The BMO system, conversely, displays strong ferromagnetic properties with a Curie temperature of 105 K but lacks robust ferroelectricity, with a Curie temperature of 760 K . The fact that these systems do not present simultaneous ferroelectric and magnetic properties is due to the converse physical requirements for the two orders.…”

Study of band structure, transport and magnetic properties of BiFeO3–TbMnO3 composite

“…An alternate option is to prepare composite of different multiferroic materials with a similar structure involving BiFeO 3 . There are reports on composite structures and superlattice structures of BiFeO 3 -BaTiO 3 , BiFeO 3 -PbTiO 3 , and BiFeO 3 -BiMnO 3 , showing improvement in multiferroic properties [23][24][25]. Yu et al [26] have reported exchange bias and other enhanced magnetic properties in BiFeO 3 -La 0.7 Sr 0.3 MnO 3 heterostructure due to charge transfer-assisted band reconstruction near the interface which in turn creates additional ferromagnetic and antiferromagnetic exchange interactions.…”