Magneto-optical Faraday effect in nanocrystalline oxides

Abstract

Magneto-optical materials have widespread applications in communication and optical devices. Besides existing applications such as optical diodes, untapped potential applications could be accessed should magneto-optical properties be improved such that smaller magnetic fields can be employed. Here we present an efficient method for fabricating oxide materials that possess excellent optical and magnetic properties—they are transparent to visible light yet have high magnetic susceptibility. Combined, these properties produce large Faraday rotations; the measured Verdet constant is >−300 rad T−1 m−1 at 632.8 nm, a high value for a thick, optically transparent material. Because this Verdet constant is more than twice that of the state of the art material, these nanocrystalline oxides produce polarized light rotations with less than half the applied magnetic field necessary. They are made by densifying rare earth nanocrystalline powder into dense, large-sized bodies using an electric current activated technique (sometimes known as spark plasma sintering). The processing temperature is optimized in order to achieve sufficient density without causing excessive phase changes that would destroy light transparency. This process produces materials quickly (<20 min), which, combined with high magneto-optical properties, promises less expensive, smaller, more portable magneto-optical devices.

Transmitting, emitting and controlling light: Processing of transparent ceramics using current-activated pressure-assisted densification

“…A study by Morales et al [31] on producing magnetooptical ceramics provides a good example of the use of CAPAD to make materials that require precise control of temperature, pressure and time. Morales et al densified Dy 2 O 3 in an attempt to produce ceramics whose optical properties can be controlled by external magnetic fields.…”

“…The optical symmetry and demonstrated functionality are also listed. References: MgO [15], MgAl 2 O 4 [16], YAG [18,36], YSZ [3-5,14], Y 2 O 3 [19,21,22], Lu 2 O 3 [20], Al 2 O 3 [9,10,33-35] Dy 2 O 3[31], Nd:YAG[29], Ce:YAG[28], Tb:AlN[30].…”

“…Two materials are shown to illustrate the effect of varying Verdet constant. The darker shade material represents nanoDy 2 O 3[31] with thickness t REO .…”

Broadband white light emission from Ce:AlN ceramics: High thermal conductivity down-converters for LED and laser-driven solid state lighting

“…In this work, we use a processing procedure based on Current Activated Pressure Assisted Densification (CAPAD) that has been shown to produce high quality optical ceramic for demanding optical applications. [13][14][15] Of particular importance are the high heating and cooling rates that allow for higher than equilibrium doping in ceramics. 16,17 The inset in the top left corner of Figure 1 is a picture of a CAPAD processed Ce:AlN ceramic on top of a commercial UV-LED (365 nm, LED World).…”

Producing Three Dimensional Nanostructured Magnetic Materials for Novel Magnetic Devices

“…This process produces materials quickly (<20 min), which, combined with high magneto-optical properties, promises less expensive, smaller, more portable magneto-optical devices. These results were published in Journal of Applied Physics [5] and resulted in a patent application [P1] (e) Controlling thermal transport through nanostructure…”