Room temperature ferroelectricity in fluoroperovskite thin films

Abstract

The NaMnF3 fluoride-perovskite has been found, theoretically, to be ferroelectric under epitaxial strain becoming a promising alternative to conventional oxides for multiferroic applications. Nevertheless, this fluoroperovskite has not been experimentally verified to be ferroelectric so far. Here we report signatures of room temperature ferroelectricity observed in perovskite NaMnF3 thin films grown on SrTiO3. Using piezoresponse force microscopy, we studied the evolution of ferroelectric polarization in response to external and built-in electric fields. Density functional theory calculations were also performed to help understand the strong competition between ferroelectric and paraelectric phases as well as the profound influences of strain. These results, together with the magnetic order previously reported in the same material, pave the way to future multiferroic and magnetoelectric investigations in fluoroperovskites.

Making EuO multiferroic by epitaxial strain engineering

“…A strain-induced displacive ferroelectric instability is rather surprising in ferromagnetic EuO because the permittivity and phonon frequencies are almost temperature independent in bulk EuO. Strain-induced ferroelectric phase transitions have so far been reported mainly in incipient ferroelectrics like the perovskites SrTiO 3 48 , KTaO 3 49 , EuTiO 3 14 , and NaMnF 3 9 or in related Sr n+1 Ti n O 3n 50 phases with Ruddlesden-Popper structures. In all of these bulk systems, the permittivity and soft phonons driving the ferroelectric phase transition are strongly temperature dependent and therefore they are very sensitive to strain 14,[49][50][51][52] .…”

“…Other recent successful examples are the cases of CaMnO 3 15 in which incipient ferroelectricity was observed below 25 K under 2.4% tensile strain 16 , or SrMnO 3 6 , in which a phase transition to a polar state at 380 K has been observed for 1.7% tensile strain 17 , while the antiferromagnetic transition temperature is simultaneously shifted from the bulk value of 230 K 18,19 to 180 K in the strained film 19 . Another interesting case is strained NaMnF 3 , which was predicted to be ferroelectric with a weak ferromagnetic moment from DFT simulations 8 and the multiferroic behavior was subsequently confirmed experimentally in films grown on SrTiO 3 substrates 9 .…”

“…For example, it can increase the superconducting, ferroelectric, or ferromagnetic transition temperatures, and improve microwave dielectric properties; it can even induce ferroelectric or ferromagnetic states in materials where these features are not present in the absence of strain [1][2][3][4] . This approach has been applied to enlarge the limited number of multiferroics [5][6][7][8][9] , which are simultaneously ferroelectric and (anti)ferromagnetic, with enhancement of their magnetoelectric response [10][11][12][13] .…”

Low-Voltage Permittivity Control of Coplanar Lines Based on Hafnium Oxide Ferroelectrics Grown on Silicon

“…4a and 4b: with respect to the homologous results displayed in Figs. 3a and 3b, it is evident the clearly present but less pronounced ferroelectric effect when biasing the CPW lines with −2 V and −5 V. The explanation for this phenomenon can be found in the built-in field which forms at the HRSi/HfZrO interface [20]: it is well known that this field induces an asymmetry in the ferroelectric hysteresis loop and, together with the external DC electric field, affects both ferroelectric double well potential and polarization states.…”

Defect clustering in an Eu-doped NaMgF3 compound and its influence on luminescent properties

“…Perovskite compounds are a class of special materials that have attracted wide attention in recent years for interesting applications, such as magnetoelectrics, 1,2 photovoltaics devices, [3][4][5][6] light-emitting diodes, 7,8 lasers, 9,10 photocatalysis, 11 memristors, 12 and ionizing radiation detectors. [13][14][15] Fluoroperovskite materials, ABF 3 (where A and B stand for alkali and alkaline earth metals, respectively), are a sub-class of perovskite compounds.…”