Interplay of Magnetic Properties and Doping in Epitaxial Films of h‐REFeO₃ Multiferroic Oxides

Abstract

main challenges to overcome in order to make multiferroic materials potential candidates for magnetoelectric devices is the requirement of simultaneous presence of magnetization and ferroelectricity (FE) at room temperature, which so far only rare of known multiferroics present it and weakly. [1,2] As a demand for miniaturization and device application, multiferroic thin films are potentially more relevant than bulk materials. Thin films allow interface and strain/stress engineering, which results in wide freedom to manipulate ferroic properties for customized applications. In the class of multiferroic materials with hexagonal symmetry, h-RE(Mn/Fe) O 3 (RE: Sc, Y, Ho to Lu), magnetoelectric coupling was observed below antiferromagnetic Neel ordering temperature (T N). [3] Topologically protected sixfold FE vortices the consequence of interlocking of electrical polarization to antiphase structural boundaries below paraelectric (PE) to FE phase transition temperature (T C) was widely explored in the bulk state. The complexity and rich physics of coupling magnetic and ferroelectric orders originates from the cross link of ferroic properties and unit cell distortion. Breaking the inversion symmetry of unit cell and tilting (Mn,Fe)O 5 bipyramid at phase transition temperature (T C) results in improper ferroelectricity with net electrical polarization along c-axis. [4] Geometrically frustrated Multiferroic materials demonstrating coexistence of magnetic and ferroelectric orders are promising candidates for magnetoelectric devices. While understanding the underlying mechanism of interplaying of ferroic properties is important, tailoring their properties to make them potential candidates for magnetoelectric devices is challenging. Here, the antiferromagnetic Neel ordering temperature above 200 K is realized in successfully stabilized epitaxial films of (Lu,Sc)FeO 3 multiferroic oxide. The first-principles calculations show the shrinkage of in-plane lattice constants of the unit cells of the films on different substrates which corroborates well the enhancement of the Neel ordering temperature (T N). The profound effect of lattice strain/stress at the interface due to differences of in-plane lattice constants on out of plane magnetic properties and on spin reorientation temperature in the antiferromagnetic region is further elucidated in the epitaxial films with and without buffer layer of Mn-doped LuFeO 3. Writing and reading ferroelectric domains reveal the ferroelectric response of the films at room temperature. Detailed electron microscopy shows the presence of lattice defects in atomic scale. First-principles calculations show that orbital rehybridization of rare-earth ions and oxygen is one of the main driving force of ferroelectricity along c-axis in thin films of hexagonal ferrites.