Room temperature multiferroicity in orthorhombic LuFeO3

Abstract

From the measurement of dielectric, ferroelectric, and magnetic properties we observe simultaneous ferroelectric and magnetic transitions around ∼600 K in orthorhombic LuFeO 3 . We also observe suppression of the remanent polarization by ∼95% under a magnetic field of ∼15 kOe at room temperature. The extent of suppression of the polarization under magnetic field increases monotonically with the field. These results show that even the orthorhombic LuFeO 3 is a room temperature multiferroic of type-II variety exhibiting quite a strong coupling between magnetization and polarization.PACS numbers: 75.80.+q, 75.75.+a, 77.80.-e The magnetoelectric multiferroics with strong crosscoupling between ferroelectric and magnetic order parameters have attracted a lot of attention during the last one decade because of their potential in radically enhancing the functionalities of the spintronics-based devices for many, including bio-medical, applications. 1 A room temperature multiferroic, for obvious reasons, is always the most sought-after compound. Apart from BiFeO 3 , other systems such as CuO3] have also been identified as potential high temperature multiferroic compounds. In recent time, hexagonal LuFeO 3 is found to exhibit multiferroicity at room temperature. 4 Coexistence of ferrimagnetic and ferroelectric orders was reported in orthorhombic LuFe 1−x Mn x O 3 as well. 5 However, in none of these recent work direct measurement of the multiferroic coupling has been attempted. In this Letter, we show that even the pure orthorhombic-LuFeO 3 , in bulk form, exhibits large magnetoelectric multiferroic coupling at room temperature. The remanent polarization (P r ) is suppressed by ∼95% under a magnetic field of ∼15 kOe. The extent of suppression of P r increases monotonically with the increase in magnetic field. The ferroelectric and magnetic transitions are simultaneous around ∼600 K indicating magnetic structure driven ferroelectricity. This observation signfies that the orthorhombic LuFeO 3 is a multiferroic of type-II variety.The structurally nonpolar orthoferrites such as SmFeO 3 , YFeO 3 , LuFeO 3 etc. exhibit small yet finite ferroelectric polarization because of noncollinear spin structure with canted antiferromagnetic order. [6][7][8] This magnetic order induces a spin current 9 via spinorbit-coupling driven antisymmetric exchange interaction along the Fe 3+ -O 2− -Fe 3+ pathway. The spin current ( j s ) in such a noncollinear magnetic structure breaks the a) Electronic mail: dipten@cgcri.res.in centrosymmetry of the electronic charge density distribution and yields a finite polarization ( P ∝ j s ). 9,10 These compounds, where magnetism drives ferroelectricity, belong to the type-II category of the multiferroics. Interestingly, unlike the well-known perovskite manganites such as TbMnO 3 or DyMnO 3 , the rare-earth orthoferrites exhibit the ferroic transitions at well above the room temperature. In fact, for many of these orthoferrites, the magnetic and ferroelectric transition points (T N and T C , respectively) ar...

Magnetic and dielectric properties of o-LuFeO3/SrTiO3

“…The anomaly of the intrinsic dielectric response was observed in [3] near the magnetic transition point T N~6 00 K that clearly told about a coupling between dielectric and magnetic properties in o-LuFeO 3 . In our case this anomaly has corresponded to the observed increase of ε' with increasing temperature up to 450 K. We also observed a frequency dependent maximum of permittivity near 130 K. Similar low temperature anomaly, indicating possible charge ordering in the temperature range of 150-300 K, was observed in o-LuFeO 3 ceramics in [9], assuming the preserving of the dielectric properties during the transition from bulk samples to thin films how it was in the case of magnetic properties.…”

“…Ferroelectricity transition in h-LuFeO 3 was observed below T C = 1050 K connecting from a P6 3 /mmc → P6 3 cm structure distortion [3].…”

“…The crystal structure of the hexagonal h-LuFeO 3 belongs to the space group P6 3 [3]. Ferroelectricity transition in h-LuFeO 3 was observed below T C = 1050 K connecting from a P6 3 /mmc → P6 3 cm structure distortion [3].…”

“…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 .…”

Strain effect on ferroelectric polarization of epitaxial LuFeO3 thin films

“…The LFO, which is one of the rare-earth orthoferrites, has been considered to be potential multiferroics [19,20]. Nevertheless, it has been reported that the LFO thin films showed very low ferroelectric polarizations [20][21][22].…”