Sensors and actuators on orthoferrites

Abstract

A review of magneto-optical (MO) principles applications in electric current (magnetic field) meters and angle measuring devices is presented. MO principles exhibit the advantage of both excellent electromagnetic compatibility and high bandwidth. Orthoferrites are transparent magnets characterized by a number of unique features (very high values of MO figure of merit -99% transparency for a 45° rotator at 1520 nm, and high quality factor, extremely high domain wall velocities -up to 20 km/s) promising their use for the development of various innovative microtechnological devices with improved characteristics. KeywordsYttrium orthoferrite, magneto-optical sensors, Faraday effect. INTRODUCTIONThe ability to modify parameters of light by means of magnetic field made possible development of a large family of magnetooptical (MO) sensors combining high sensitivity to the measured magnetic field with advantages of optical methods: contactless, practically unlimited frequency range, absence of potential isolation problems, etc. Concerning actuators, using of transparent magnetic materials provides opportunity to use rather low operating voltages -sometimes even zero voltages -using magnetic hysteresis phenomenon. To date the mostly used MO materials are garnets of various compositions characterized by very small value of "characteristic length" [1] in which domains of submicron widths are observed. This feature is of advantage for memory application whereas for a number of sensor applications much more wide domains are preferable. Wide domains, up to several hundred micrometer, are observed in other transparent ferromagnets -orthoferrites. Orthoferrites possess very high values of magnetooptical figure of merit (ratio of the specific Faraday rotation to absorption) especially at the fiberoptic wavelengths, very high domain wall (DW) mobility. In orthoferrites domain walls (DWs) can move with cosmic velocities -up to 20 km/s [2, 3]. Magnetization of orthoferrites can be redirected within 5 picoseconds [4]. These outstanding properties make orthoferrites very attractive for a wide variety of applications. In this paper results of our works on development of sensors of electric current (magnetic field), and of light spot po sition as well as of the optical switch are presented.

Influence of Synthetic Conditions on the Crystal Structure, Optical and Magnetic Properties of o-EuFeO3 Nanoparticles

“…Powder X-ray diffraction (PXRD) was applied in determining the phase composition and crystal structure of the obtained powders using an EMPYREAN X-ray diffractometer with Cu Kα radiation (λ = 1.5406 Å) using a step of 0.019 • and a Bragg angle (2θ) of 10-80 • . The average size of crystals (D) was determined according to the Scherrer equation (Equation (1)). The unit cell volume (V) of crystals was the product of lattice parameters (a, b, and c) obtained from the Profex XRD application.…”

“…To date, nanomaterials based on orthoferrites with the general formula RFeO 3 (R = Sc, Y, and Ln) have received increased attention due to their attractive perovskite-like structure, high values of the magnetooptical ratio of the specific Faraday rotation to absorption, and high domain wall mobility [1] as well as strong visible-light absorbance [2] and luminescent properties [3], etc. These properties make them fascinating in various innovative applications such as sensors and actuators [1], gas sensing devices [4], potential MRI contrast agents [5], multiferroic materials [6][7][8], catalysts for toluene oxidation [9,10], and photocatalysts in the degradation of various water-soluble dyes [11], Congo red molecules [12], and methyl orange [13,14].…”

Shape controllable synthesis of NdFeO3micro single crystals by a hydrothermal route

“…Controlled synthesis of well-defined inorganic crystals with uniform dimensions and shapes is of extraordinary importance because of the size and morphology dependencies of magnetic, catalytic and gas sensitivity properties. 1,2 Rare earth orthoferrites, having the chemical formula RFeO 3 (where R refers to one or more rare-earth elements), represent a particularly interesting class of materials due to their dielectric, 3,4 magnetic, 5 magneto-optical, 6,7 multiferric, [8][9][10] magnetoelectric, 11 catalytic, 12,13 and gas sensitivity properties. 14 We are, in particular, interested in NdFeO 3 which has been employed in major applications such as gas sensors [15][16][17][18] and catalysts.…”

Hyperfine and magnetic properties of a YxLa1−xFeO3 series (0≤x≤1)

“…In most cases, they crystallize in a perovskite-type structure, with corner-sharing FeO 6 octahedra and A cations occupying the center of a cube (generally with an orthorhombic or rhombohedral distortion) [1]. From a technological point of view, materials based on orthoferrites are interesting because they can be used in a wide range of applications: sensors, catalysts, solid oxide fuel cells, etc [2][3][4]. Their functional properties (electrical conductivity, magnetization, catalytic activity) are very dependent on the structure, which can be significantly modified through the incorporation of cations with different sizes and charges [5][6][7].…”