Magnetic and dielectric properties of o-LuFeO₃/SrTiO₃

Abstract

Abstract.Here we present the investigation of the orthorhombic o-LuFeO 3 thin film grown on SrTiO 3 (001) substrate. Temperature dependencies of magnetization measured in magnetic fields 1000 Oe and 2000 Oe were described in the assumption that ferromagnetic correlated regions are presented in samples together with the paramagnetic phase. Additional argument in favor of the ferromagnetic regions existence in o-LuFeO 3 is the magnetic hysteresis curve measured at T=5 and 100K. The temperature dependences of dielectric response were measured and analyzed. IntroductionThe LuFeO 3 can be crystalized in two modifications: hexagonal and orthorhombic. Thin films of the hexagonal LuFeO 3 (h-LuFeO 3 ) deposited on Al 2 O 3 and YSZ are a multiferroic material that exhibits spontaneous electric and magnetic polarizations simultaneously [1,2], which have great importance for future technologies. The orthorhombic crystallographic structure o-LuFeO 3 is the thermodynamically stable with standard condition preparation [3], the hexagonal structure is metastable. The free energy of o-LuFeO 3 is a few lower than that of the h-LuFeO 3 . In epitaxial thin films, the film-substrate interfacial energy may favor the h-LuFeO3 structure, if the symmetry of the substrate is triangular or hexagonal. This effect can stabilize the hexagonal structure in epitaxial thin films, to a certain critical thickness [1, 4] Therefore, when LuFeO 3 is deposited onto substrate in the form of thin film it can coexist in the form of hexagonal and orthorhombic domains that was established in work [4] where two structural phases of LuFeO 3 occurs on a length scale of micrometer, as visualized in real space using X-ray photoemission electron microscopy, and moreover, there is the structural transition at about 1000 o C, from the hexagonal to the orthorhombic phase of LuFeO 3 [4] and then it results to interesting physical properties.The crystal structure of the hexagonal h-LuFeO 3 belongs to the space group P6 3 cm with lattice parameters a = b = 5.993 Å, c = 11.634 Å and α=β=90 o , γ=120

Multiferroic h-LuFeO3 Thin Films on (111) and (100) Surfaces of YSZ Substrates: An Experimental and Theoretical Study

“…Indeed, in accordance to our previous study, the hexagonal modification of LuFeO 3 tends to grow with the [001] direction being perpendicular to the YSZ(111) substrate plane, while new experimental results have shown that h-LuFeO 3 grows likewise on the YSZ(100) surface. The growth of epitaxial thin films of orthorhombic modification of LuFeO 3 still remains poorly investigated. , However, the growth of orthorhombic rare-earth manganates is currently far better studied. It was shown that orthorhombic manganates tend to grow with their pseudocubic [110] p direction perpendicular to the YSZ(100) surface and, since rare earth manganates and orthoferrites are isostructural, it seems to be reasonable to use these data as a starting point for the research.…”

“…The growth of epitaxial thin films of orthorhombic modification of LuFeO 3 still remains poorly investigated. 15,33 However, the growth of orthorhombic rare-earth manganates is currently far better studied. It was shown that orthorhombic manganates tend to grow with their pseudocubic [110] p direction perpendicular to the YSZ(100) surface 34 and, since rare earth manganates and orthoferrites are isostructural, it seems to be reasonable to use these data as a starting point for the research.…”

“…It should be noted that, in conditions of a common solid-state synthesis, rare-earth ferrites (REFeO 3 ) form in the thermodynamically stable structure of the orthorhombically distorted perovskite ( Pnma ), which is a simple antiferromagnetic with only a hint of the ferroelectric order . Yet, the hexagonal modification may be stabilized in the shape of thin film on a surface with the certain symmetry .…”

“…It should be noted that, in conditions of a common solidstate synthesis, rare-earth ferrites (REFeO 3 ) form in the thermodynamically stable structure of the orthorhombically distorted perovskite (Pnma), which is a simple antiferromagnetic with only a hint of the ferroelectric order. 15 Yet, the hexagonal modification may be stabilized in the shape of thin film on a surface with the certain symmetry. 16 Now, it is claimed that matching (coherent) symmetries of the coincident sites lattices (CSL) of a substrate and a film along with the optimal film/substrate crystal lattice misfit is the key to the formation of h-REFeO 3 phases and its epitaxial growth along the c axis.…”

Composition‐Dependent Ferroelectricity of LuFeO3 Orthoferrite Thin Films

“…[26] A metastable hexagonal LFO phase was found to be ferroelectric due to its noncentrosymmetric crystal structure, with T C = 1020 K and P r up to ≈10 µC cm −2 at room temperature. [27][28][29] Both orthorhombic and hexagonal LFO phases have been grown in the form of thin films using pulsed laser deposition (PLD), [25,27,30] radio frequency magnetron sputtering, [31,32] or molecular beam epitaxy. [28] When the two phases are grown together, the film can show multiferroicity with a magnetization of ≈0.24 µ B per f.u.…”