Spintronic 3D Microchip Developed

A new type of microchip based on spintronic technology was created that not only moves information from left to right and back to front, but up and down as well.

In electronics, semiconductors utilize the electrical charge carried by the electron. It carries either a positive charge or negative charge. Information is based on the charge of these electrons.

Aside from the electrical charge, electrons also has another property; its spin. The spin of an electron makes it behave like a bar magnet. It either points up or down. Spintronic technology takes advantage of this property to add one more component in storing information in an electron. Aside from the charge which could either be positive or negative, it can also carry information based on the spin which is either up or down.

Spintronic devices act according to the following scheme:

1. Information is stored (written) into spins as a particular spin orientation (up or down).
2. The spin, being attached to mobile electrons, carry the information along a wire.
3. The information is read at a terminal.

The spin orientation lasts longer than electron momentum (nanoseconds -10x^-9 compared to femtoseconds -10x^-15). This makes it optimal for applications such as memory storage and magnetic sensors applications.

Because of the efficiency in storing and transmitting information, spintronic based devices are smaller, cheaper, stable and more accurate than existing conventional devices. At the moment, some hard drives use this technology in data storage.

Higgs Transition of Monopoles Open Up Huge Possibilities In Spintronics

A magnetic monopole is a particle that has only one magnetic pole (a north pole without a south pole or a south without a north).

This particle is still hypothetical and is considered an isolated magnet because of its properties. In more technical terms, this particle would have a net "magnetic charge". Theories such as the Grand Unified Theory and the Super string theory predicts the existence of magnetic monopoles but its existence is still inconclusive. Effective (non-isolated) magnetic monopole quasi-particles exist in some condensed matter systems such as Spin Ice.

Spin Ice

A spin ice is a substance that can never be completely frozen. It is similar to iced water or water ice. It has this property because it does not have a single minimal-energy state. This is called geometric fractionalization or frustration. A spin ice has "spin" degrees of freedom (i.e. it is a magnet), with frustrated interactions which prevent it freezing.

Existence of deconfined magnetic monopoles in these materials were gathered from experiments. It was shown to behave with properties similar to the hypothetical magnetic monopoles postulated to exist in the vacuum.

Higgs transition of north and south poles of electrons in a magnet

Minimal evidence of a Higgs transition 1 of north and south poles of electron spins was observed in a magnet Yb2Ti2O7 at the absolute temperature 2 0.21 K. A fractionalization of these monopoles from electron spins was observed on cooling to 0.3 K. On further cooling below 0.21 K, the material showed the ferromagnetism to be understood as a superconductivity of monopoles. The work is reported in an online science journal "Nature Communications" in UK on August 7, by an international collaboration team of Dr. Shigeki Onoda (Condensed Matter Theory Lab., RIKEN Advanced Science Institute), Dr. Lieh-Jeng Chang (Quantum Beam Science Dictorate, Japan Atomic Energy Agency and Dept. of Physics, National Cheng Kung Univ.), and Dr. Yixi Su (Jülich Center for Neutron Science JCNS-FRM II, Forschungszentrum Jülich), and coworkers.

Figure one shows the pyrochlore lattice structure of spin ice and spins on a tetrahedron. The left shows Pyrochlore lattice structure. Each lattice point (red) hosts an electron spin. The right shows Directions and configurations allowed for spins located at vertex points of the unit tetrahedron of the pyrochlore lattice structure.
Credit: RIKEN

Electrons rotate like the earth, acting as tiny magnets called spins in magnetic materials. Usually, these spins form a magnetic order on cooling, and the monopoles, namely, north and south poles of electron spins, are confined to each other. In magnetic materials called spin ice 3, the spins remain unordered even at low temperatures, and the monopoles behave as if they are fractionalized while unstable. Since 2010, on the other hand, Dr. Onoda and coworkers have predicted a so-called quantum spin ice 4 that can exhibit a magnetic order realized by a Bose-Einstein condensation of monopoles. In this case, a coupling to fictitious electromagnetic fields, called gauge fields, endows a mass for otherwise gapless spin excitations in the ordered state, forming an analogous superconducting state of monopoles via the Higgs mechanism5. Now, cooling a quantum spin ice material Yb2Ti2O7 to 0.21 K, the team observed a transition from a state with fractionalized unstable monopoles to a ferromagnetic state with condensed stable monopoles, indicating a Higgs transition of monopoles. This state hosting dissipationless monopole current of spins is expected to play important roles in spintronics that aims at efficient controls of magnets for application.

1. Background

In most of electrically insulating magnets, electrons form tiny magnets called spins by their rotation. A macroscopic number of spins usually show an order at low temperatures, demonstrating a spontaneous symmetry breaking. For instance, in ferromagnets and antiferromagnets, spins show parallel and antiparallel alignments, respectively. However, a geometrical frustration, which will be explained below, sometimes suppresses a formation of the magnetic order, as in materials called spin ice, Dy2Ti2O7 and Ho2Ti2O7.

New OLED Developed: Spin Polarized Organic LED (Spin OLED)

Demonstration of a conventional flexible OLED device

Light Emitting Diodes (LED) uses a standard semiconductor to generate light in different colors. Organic Light Emitting Diodes (OLED) uses an organic polymer or plastic semiconductors to generate light.

They produce light on their own, do not generate heat, and are thin and flexible.

OLEDs are currently used as display units in small devices such as mobile phones, digital cameras, and MP3 players. Not to be confused with LCD screens, these type of dispaly screens do not need to be backlit with LEDs or lamps.

Some commercial visual displays also use OLED screens. Most of these screens use AMOLED (Active Matrix OLED) technology as they have a higher resolution than Passive Matrix OLEDs. An AMOLED screen has a thin-film transistor that switches each individual pixel on or off giving it better control and clarity of the image. Current manufacturing costs are what hinders this type of screen of breaking into the

University of Utah physicists invent 'spintronic' LED

University of Utah physicists invented a new "spintronic" organic light-emitting diode or OLED that promises to be brighter, cheaper and more environmentally friendly than the kinds of LEDs now used in television and computer displays, lighting, traffic lights and numerous electronic devices.

"It's a completely different technology," says Z. Valy Vardeny, University of Utah distinguished professor of physics and senior author of a study of the new OLEDs in the July 13, 2012 issue of the journal Science. "These new organic LEDs can be brighter than regular organic LEDs."

The Utah physicists made a prototype of the new kind of LED – known technically as a spin-polarized organic LED or spin OLED – that produces an orange color. But Vardeny expects it will be possible within two years to use the new technology to produce red and blue as well, and he eventually expects to make white spin OLEDs.

However, it could be five years before the new LEDs hit the market because right now, they operate at temperatures no warmer than about minus 28 degrees Fahrenheit, and must be improved so they can run at room temperature, Vardeny adds.

Spin Seebeck Effect Lead To Engines With No Moving Parts And Infinitely Reliable

Schematic illustration of the spin-Seebeck effects
Credit: Tohoku University

The Seebeck effect is a phenomenon in which a temperature difference between two dissimilar electrical conductors or semiconductors produces a voltage difference between the two substances. It is simply the conversion of the temperature differences directly into electricity.

This effect is named for German-Estonian physicist Thomas Johann Seebeck who discovered it in 1821.

Physicists in 2008, discovered what they are calling the spin Seebeck effect. The spin Seebeck effect is seen when heat is applied to a magnetized metal. As a result, electrons rearrange themselves according to their spin. Unlike ordinary electron movement, this rearrangement does not create heat as a waste product.

This development can lead to the manufacturing of faster, more efficient microchips and open up a new class of devices called spintonics devices.

Researchers 1 step closer to new kind of thermoelectric 'heat engine'

Researchers who are studying a new magnetic effect that converts heat to electricity have discovered how to amplify it a thousand times over - a first step in making the technology more practical.

In the so-called spin Seebeck effect, the spin of electrons creates a current in magnetic materials, which is detected as a voltage in an adjacent metal. Ohio State University researchers have figured out how to create a similar effect in a non-magnetic semiconductor while producing more electrical power.

They've named the amplified effect the "giant spin-Seebeck" effect, and the university will license patent-pending variations of the technology.

The resulting voltages are admittedly tiny, but in this week's issue of the journal Nature, the researchers report boosting the amount of voltage produced per degree of temperature change inside the semiconductor from a few microvolts to a few millivolts - a 1,000-fold increase in voltage, producing a 1-million-fold increase in power.