eNewsletter

September 2009

Let There Be Light: Teaching Magnets to Do More Than Just Stick Around
That palm tree magnet commemorating your last vacation is programmed for a simple function – to stick to your refrigerator. Similarly, semiconductors are programmed to convey bits of information small and large, processing information on your computer or cell phone.

Scientists are working to coax those semiconductors to be more than conveyers, to actually perform some functions like magnets, such as data recording and electronic control. So far most of those effects could only be achieved at very cold temperatures: minus 260 degrees Celsius or more than 400 below zero Fahrenheit, likely too cold for most computer users.

However, researchers led by a University of Washington chemist report Friday (Aug. 21) in Science that they have been able to train tiny semiconductor crystals, called nanocrystals or quantum dots, to display new magnetic functions at room temperature using light as a trigger.

Silicon-based semiconductor chips incorporate tiny transistors that manipulate electrons based on their charges. Scientists also are working on ways to use electricity to manipulate the electrons' magnetism, referred to as "spin," but are still searching for the breakthrough that will allow "spintronics" to function at room temperature without losing large amounts of the capability they have at frigid temperatures.

The team led by Daniel Gamelin, a UW chemistry professor, has found a way to use photons, tiny light particles, to manipulate the magnetism of semiconductor nanocrystals efficiently, even up to room temperature.

"This provides a completely new approach to microelectronics, if you can use spin instead of charge to process information and use photons to manipulate that process," Gamelin said. "It opens the door to materials that store information and perform logic functions at the same time without the need for super cooling."

The team used nanocrystals of a cadmium-selenium semiconductor called cadmium selenide, but replaced some nonmagnetic cadmium ions with magnetic manganese ions. The crystals, smaller than 10 nanometers across (a nanometer is one-billionth of an inch), were then suspended in a colloid solution, like droplets of cream suspended in milk.

Beams of photons were used to align all of the manganese ions' spins, creating magnetic fields as much as 500 times more powerful than in the same semiconductor material without manganese. The magnetic effects were strongest at low temperatures, but remained remarkably strong up to room temperature, Gamelin said.

Besides Gamelin, authors of the Science paper are Rémi Beaulac and Paul Archer of the UW and Lars Schneider and Gerd Bacher of the University of Duisburg-Essen in Germany.

In a second paper published, Gamelin's group reported related effects in semiconductor nanocrystals made of zinc oxide but also containing small amounts of manganese impurities.

With zinc oxide, photons acted more as an on-off switch – once photons altered the zinc oxide's magnetism, the photon stream could be removed and the effect remained in place until another stimulus was applied to turn the effect off again.

Besides Gamelin, authors of the Nature Nanotechnology paper are Stefan Ochsenbein, Yong Feng, Kelly Whitaker, Ekaterina Badaeva, William Liu and Xiaosong Li, all of the UW.

Some behaviors described in the papers have been seen previously at very low temperatures, but in those cases the active materials were embedded in other crystals and so could not be isolated or processed. Suspending the nanocrystals in a colloid solution brings the magnetic effects into a new functional form that could be useful for integration with unconventional materials, Gamelin said. For example, the solution containing the crystals could be applied to a film using a device like an ink jet printer, or interfaced with carbon-based materials using techniques not typically practical for magnetic semiconductors.

"We've brought these spin effects into a processable form," he said. "I think both of these papers are converging on the same applications. We're exploring how to manipulate spins in these nanostructures and perhaps opening the door for some exciting new technologies."

Funding for the work in the two papers came from the US National Science Foundation, the Dreyfus Foundation, the Sloan Foundation, the Natural Sciences and Engineering Research Council of Canada, the German Research Foundation, Gaussian Inc., the Research Corp., the Swiss National Science Foundation and the University of Washington.

Unexpectedly Long-Range Effects in Advanced Magnetic Devices
A tiny grid pattern has led materials scientists at the National Institute of Standards and Technology (NIST) and the Institute of Solid State Physics in Russia to an unexpected finding—the surprisingly strong and long-range effects of certain electromagnetic nanostructures used in data storage. Their recently reported findings* may add new scientific challenges to the design and manufacture of future ultra-high density data storage devices.

The team was studying the behavior of nanoscale structures that sandwich thin layers of materials with differing magnetic properties. In the past few decades such structures have been the subjects of intense research because they can have unusual and valuable magnetic properties. The data read heads on modern high-density disk drives usually exploit a version of the giant magnetoresistance (GMR) effect, which uses such layered structures for extremely sensitive magnetic field detectors. Arrays of nanoscale sandwiches of a similar type might be used in future data storage devices that would outdo even today’s astonishingly capacious microdrives because in principle the structures could be made even smaller than the minimum practical size for the magnetic islands that record data on hard disk drives, according to NIST metallurgist Robert Shull.

The key trick is to cover a thin layer of a ferromagnetic material, in which the magnetic direction of electrons, or “spins,” tend to order themselves in the same direction, with an antiferromagnetic layer in which the spins tend to orient in opposite directions. By itself, the ferromagnetic layer will tend to magnetize in the direction of an externally imposed magnetic field—and just as easily magnetize in the opposite direction if the external field is reversed. For reasons that are still debated, the presence of the antiferromagnetic layer changes this. It biases the ferromagnet in one preferred direction, essentially pinning its field in that orientation. In a magnetoresistance read head, for example, this pinned layer serves as a reference direction that the sensor uses in detecting changing field directions on the disk that it is “reading.”

Researchers have long understood this pinning effect to be a short-range phenomenon. The influence of the antiferromagnetic layer is felt only a few tens of nanometers down into the ferromagnetic layer—verticallly. But what about sideways? To find out, the NIST/ISSP team started with a thin ferromagnetic film covering a silicon wafer and then added on top a grid of antiferromagnetic strips about 10 nanometers thick and 10 micrometers wide, separated by gaps of about 100 micrometers. Using an instrument that provided real-time images of the magnetization within grid the structure, the team watched the grid structure as they increased and decreased the magnetic field surrounding it.

What they found surprised them.

As expected, the ferromagnetic material directly under the grid lines showed the pinning effect, but, quite unexpectedly, so did the uncovered material in regions between the grid lines far removed from the antiferromagnetic material. “This pinning effect extends for maybe tens of nanometers down into the ferromagnet right underneath,” said Shull, “so you might expect that there could be some residual effect maybe tens of nanometers away from it to the sides. But you wouldn’t expect it to extend 10 micrometers away—that’s 10 thousand nanometers.” In fact, the effect extends to regions 50 micrometers away from the closest antiferromagnetic strip, at least 1,000 times further than was previously known to be possible.

The ramifications, says Shull, are that engineers planning to build dense arrays of these structures onto a chip for high-performance memory or sensor devices will find interesting new scientific issues for investigation in optimizing how closely they can be packed without interfering with each other.

* Y.P. Kabanov, V.I. Nikitenko, O.A. Tikhomirov, W.F. Egelhoff, A.J. Shapiro and R.D. Shull. Unexpectedly long-range influence on thin-film magnetization reversal of a ferromagnet by a rectangular array of FeMn pinning films. Physical Review B 79, 144435, 2009. DOI: 10.1103/PhysRevB.79.144435.

New Surface Mount Magnetic Reed Switch Features Unparalleled Sensitivity
Standex Electronics has introduced the SR4J series of ultra small surface mount magnetic reed switch for non-contact position sensing. Over molded around a proven GR200 magnetic reed switch, this J leaded version measures 6.8 mm in length and 2.41 mm in height. The external leads of the reed switch form a tear drop terminal pad arrangement, which preserves a greater portion of the initial magnetic circuit, thus enhancing the magnetic sensitivity of the sensor. The SR4J series boasts a maximum sensitivity range of 3/5 Ampere Turns (AT) (initial), and is available in a production range from 3 to 20 AT. 

In addition to a small footprint and tight sensitivity range, the SR4J series is responsive – with a typical operating time of 0.2 milliseconds, and release time of 0.1 milliseconds (typical).  They have a power rating of 1 VA maximum.  A switching current (Max) of 0.05 amp, DC is standard, as is a carry current rating (max) of 0.5 amp, DC.  Having an operating range of -40°C to 125°C, the SR4J is well suited for use wherever small size and sensitivity are required for non-contact position sensing applications.    

“Our unique production process delivers very tight magnetic sensitivity ranges, which allow design engineers to use the SR4J in environments with very low magnetic fields” said Standex VP Tom Gould.  “Plus the tight sensitivity range of 3-to-5 Ampere Turns is unique within the industry.” 

Murata Electronics New Chip Ferrite Beads Offer Lower DC Resistance
Murata Electronics North America has introduced the BLM15AX_SN series, an advanced ferrite bead that lowers DC resistance by up to 60 percent compared to previous models. As part of Murata's expanding electromagnetic interference filter (EMIFIL) line, the chip ferrite bead was developed with new ceramic materials and processing technologies that improve performance and reduce size in order to provide power and space savings in portable electronics.

"Power reduction is now just as critical as space reduction when it comes to designing components for handheld devices," said Deryl Kimbro, group product manager for Murata Electronics North America. "Murata's ability to provide our customers with advanced components that meet these important criteria is fully demonstrated in the new chip ferrite bead series."

Compared to its predecessors, the BLM15AX_SN chip ferrite bead has DC resistance as low as 0.02 W, a reduction of 60 percent, while the corresponding maximum rated current has increased from 1,000 mA to 1,740 mA. The series' low DC resistance also helps reduce power consumption for battery-powered applications. Developed in a compact 0402-size package (1.0 mm by 0.5 mm by 0.5 mm), it is well suited for designers seeking to reduce board space without performance degradation in portable equipment.  The ferrite bead's wide impedance ranges from 10 W to 1000 W, with an operating temperature range of -55ºC to 125ºC.

The BLM15AX_SN series is available for 0.016 cents and lead times are approximately six to eight weeks. 

Radial Leaded Inductors Deliver Reliable EMI/RFI Protection
Designed for accuracy and economy, the new Model DR217 series radial leaded inductors from Datatronic Distribution, Inc., combine improved performance, reliability and long-life.

The ROHS compliant DR217 radial leaded inductors provide improved protection against challenging EMI/RFI problems in current handling applications up to 8.4 amps. The DR217 series offers extended life in temperatures ranging from -20°C to 80°C.

The DR217 series is designed for EMI filters and switching power supplies. Combining durability with high performance, the DR217 series is well suited for commercial and industrial equipment including computers, telecom equipment, power supplies, industrial machinery, factory automation equipment, instrumentation and more.

Depending on the specific model, the DR217 series inductors feature an inductance range from 1.0 μH to 150 mH.   The DCR is specified from 0.008 to 520 Ohms maximum over a maximum current rating from 8.4 to 0.045 amps.  The DR217-0 through DR217-7 series have minimum Q specifications based on test frequencies from 25.2 kHz to 7.96 MHz.

With its through-hole wire wound coil design, the DR217 series inductors come in round packages sized from 0.196 inch (5.0 mm) diameter to 0.551 inch (14.0 mm) diameter, with lead spacing from 0.78 inch (2.0 mm) to 0.295 inch (7.5 mm) depending on the specific model. They are compatible with high-speed assembly equipment, and they are suitable for high-temperature soldering.  Tinned leads with leaded solder are also available.

Model DR217 series inductors are priced from $0.075 to $0.22 each in typical production volumes.  Lead-time is six to eight weeks.  Volume OEM pricing is available upon request.  Custom designed DR217 series radial leaded inductors can be specified to meet unique circuit requirements.

Allegro MicroSystems Releases New 8 A H-Bridge Motor Driver
Allegro MicroSystems, Inc. has released a new 8 A H-bridge DC brush motor driver integrated circuit. The dual interface that controls the H-bridge output simplifies the communication between the integrated circuit and the controller circuit. Combining low-power CMOS-compatible logic with high-current, high-voltage power MOSFET outputs, Allegro’s  STA6940M provides complete control and drive for brush DC motor applications. It provides internal fixed off time, pulse-width modulation (PWM) control of the output current and is rated at a normal operating level of 4 A. This new device is targeted at the office automation and industrial markets.

The CMOS logic section provides four modes of operation: forward and reverse normal drive rotation, outputs-off free spin (coast) and electronic braking. The innovative multi-chip internal structure separates the main logic IC (MIC) from the four N-channel power MOSFETs resulting in lower thermal resistance and greater efficiency. PWM control allows constant-current control of the output while reducing heat generation and power losses by providing fixed off-time dual decay modes. The internal charge pump ensures full power availability for switching.
It is available in a small, ZIP type 18-pin fully-molded package, which allows for additional simple heat-sinking consuming limited PCB board space.  It is priced at $3.60 in quantities of 1,000 and has an 8-week typical lead-time to market.

Neodymium Magnets With Adhesive Add Easy Pull-Tab Save Time And Labor
Adams Magnetic Products Co. has expanded its Neodymium (Neo) magnetic products by offering these powerful, compact magnetic discs with adhesive backing and a new, easy pull-tab. The liner covering the adhesive on these strong TabMAG Neo magnets has a protruding tab for easy removal. Once removed, the adhesive is exposed and the magnet can be quickly applied to packaging, displays, fixtures and other closure or presentation applications.
 
"Designed to save time and effort, this is definitely a less labor-intensive option and a blessing for those with poor dexterity," says Kerry Buntrock, Adams' general manager. "Whether clearly visible or completely hidden from view, magnets offer near limitless potential for creating convenient, durable and re-useable high-end packaging that carry a company's brand far beyond the initial product purchase."

He adds, "In signage and displays, magnets allow for fast, neat updates with minimal tools and no training. Suitable for a variety of surfaces, magnets provide the strength and durability of mechanical closures and fasteners, with the mobility of temporary hangers."

Ensuring long-lasting performance, these new TabMAG Neo magnets are nickel coated to protect against corrosion and operate in temperatures up to 176ºF. Also formulated for high temperatures and solvent resistance, the 3M Adhesive Transfer Tape 467MP is engineered for general industrial joining. Supplied in Neo grade 3512 with BHmax strength of 33-36. Adams' TabMAG Neo discs with adhesive are stocked in 0.375-, 0.500- and 0.750-inch diameters.

For perfect alignment with magnet-to-magnet applications, North Pole and South Pole options are available. The South Pole magnets are marked for easy identification and matching during production.

Energy-Efficient Chokes for Inverters in Wind Turbines Offer Low-Loss, Low Stray Fields and Compact Design
SMP Sintermetalle Prometheus (SMP) has introduced chokes for inverters in wind turbines. These inductive components feature low losses, low stray fields, a compact design and energy efficiency for the power inverters based on these chokes. SMP uses core materials made of powder composites that are specifically engineered for each individual application.

“The direct current from the modules must be converted into a sinusoidal waveform with the values required by the grid. The converter’s filters, which consist of capacitors and filter chokes, ensure that the current being fed into the grid exhibits a near sinusoidal waveform,” said Stefan Schauer, technical sales manager at SMP.

To meet the ever more demanding requirements of modern wind turbines, SMP has developed high-performance, low-loss chokes. Developed by SMP especially for inverters used in wind turbines, the materials used have low magnetostriction and low eddy current and hysteresis losses. This means that the inverters in which they are used are highly efficient, so that a larger proportion of the generated power can be fed back into the grid.  This results in a faster return of investments.

“The profitability of a wind turbine is directly related to the efficiency of the inverters, which, in turn, is determined by the energy efficiency of the components used,” said Stefan Schauer. “The manufacturers pay very close attention to the components’ efficiency, which must be as high as possible.”

In addition to low losses, components in power converters are required to have low-intensity stray fields. SMP chokes achieve this through an encapsulated design. This offers the advantage that other components can be placed in close vicinity to the chokes without the risk of magnetic interaction. Compact choke design is another important aspect. In comparison to conventional designs, SMP chokes occupy 25 percent less space.

The chokes are maintenance-free and have a long lifespan,  a significant contribution to reducing the expensive maintenance of wind turbines. SMP chokes have also been tested and approved for use in offshore installations.

For use in photovoltaics, railway engineering, drives, power electronics, power generation, instrumentation and control, SMP supplies inductive components for frequencies up to 200 kHz and current ratings up to 1,000 amperes. Depending on their application, they are constructed either as single-conductor choke for high-current applications, 1 ph individual chokes, 3 ph choke modules, or LC filters. These components offer a high energy storage capacity in a compact and cost-conscious design as well as reduced losses and improved EMC characteristics. SMP manufactures all components to customer specifications using in-house developed powder composites. All products are RoHS- and REACH-compliant and the materials used are UL-listed. To allow for a wide range of requirements, components can be made to all common international standards.

austriamicrosystems Announces its New Easypoint Joystick Module Based on Contactless Sensing Technology
austriamicrosystems, a designer and manufacturer of high performance analog ICs for automotive, communication, industrial and medical applications, has unveiled EasyPoint, a joystick module aimed at portable communication devices.

EasyPoint consists of a mechanical stack incorporating a navigation knob with a magnet and the AS5011, a contactless sensing IC. Its simple construction, and the contactless sensing technique implemented by the AS5011, means that the module offers very high mechanical reliability. The EasyPoint joystick modules support true 360° range of movement, encompass a “select” function and can be housed in a variety of form factors,
with a module height as low as 1.8 mm.

At the core of the EasyPoint joystick module is austriamicrosystems’ AS5011, a magnetic encoder IC that monitors knob displacement relative to its center position and provides position information via I2C outputs. The AS5011 offers user-selectable power-saving modes and is available in an ultra-thin QFN package (5 mm by 5 mm, 0.55 mm high).

“With EasyPoint joystick module technology, we are providing a highly reliable module for use in a variety of portable communication devices. Besides its high reliability, our solution also offers a high degree of usability. The user can move a cursor at any angle, change the speed at which the cursor moves, or select items and drag them
across the screen,” said Matjaz Novak, director of Marketing Industry & Medical at austriamicrosystems. EasyPoint joystick module demonstration units and the AS5011 IC are available for sampling. The modules come in two mechanical versions, either as a complete module with integrated AS5011 IC, or as a mechanical module only. The sizes range from 12.5 mm by 12.6 mm to 18.6 mm by 22.6 mm and support 1 mm and 2 mm knob displacement, respectively.

Azure Dynamics Awarded Two New Patents
Azure Dynamics Corp., a developer of state-of-the-art green technologies that address environmental and cost issues for the commercial transportation industry, has earned two new patents for innovations for its proprietary hybrid electric drive trains. Azure Dynamics broad patent portfolio includes 21 total patents issued or pending. The newest additions address key value-adding components applicable to electric, hybrid and PHEV vehicle drive trains.

"Azure Dynamics is a technology-driven company that continually seeks new solutions to improve hybrid electric transportation in the commercial vehicle sector," said Ron Iacobelli, Azure's chief technology officer. "These new patents further the company's position as a leading innovator in power electronic components and motor controllers that advance our technology and, ultimately, its value to our end user customers by improving performance of the vehicle control system."

The first new patent (US patent # 7,560,895) relates to indirect rotor resistance estimation system and method. This method provides a way of sensing the rotor temperature of an AC induction motor without requiring any additional hardware in the motor or inverter. "With this invention, an indirect rotor temperature measurement can be obtained and continuously updated during the operation of the motor. A good estimation of the rotor temperature allows for more accurate torque control, faster torque response, improved efficiency and improved thermal protection," said Beat Arnet, Azure Dynamics director of Hybrid Power Electronics.

The second new patent (US patent # 7,561,008) relates to a filter package that includes a pair of spaced circuit boards with a magnetic core between the circuit boards. This invention resulted from the realization that a smaller, lighter, compact filter can be achieved by packaging the core between a pair of circuit boards with the core windings interconnected to/through the circuit board(s).

"We applaud our engineering team's contributions as it continues to advance hybrid and electric vehicle technology," said Iacobelli. "The addition of these two patents along with our pending portfolio of work continues to enhance our leadership position in technology in our space and further demonstrates the breadth and experience in our technical team with patents ranging from vehicle level hybrid controls down to power electronics hardware controls and battery management."

The new technologies and hardware will be incorporated into the Azure Balance Hybrid Electric drive train currently in operation for both delivery truck and shuttle bus fleets. The Balance Hybrid Electric can improve fuel economy by 30 percent, reduce maintenance costs by 30 percent and reduce greenhouse emissions by 30 percent. With its electric-launch assist, engine-off at idle and regenerative braking, the Azure Balance Hybrid Electric has become a preferred solution for fleet managers looking to reduce overhead costs and lessen environmental impact.

IBM Fellow Stuart Parkin Wins IUPAP Magnetism Award and Neel Medal
At the International Conference on Magnetism in Karlsruhe, Germany, IBM Fellow Stuart Parkin received the International Union of Pure and Applied Physics Magnetism award and the Louis Neel Medal for his pioneering work and fundamental contributions to the development of spintronic nano-materials and nano-devices for magnetic sensing, memory and logic devices.

The IUPAP Magnetism Award and Neel Medal are presented every three years to a scientist who has made an outstanding contribution to the field of magnetism. The award winner is selected by a committee composed of the members of the IUPAP International Commission on Magnetism (C9), together with past recipients of the award.

The Neel medal, established in 1993 in recognition of the scientific achievements of Louis Eugene Felix Neel, who shared the 1970 Nobel Prize in Physics for his fundamental research and discoveries concerning antiferromagnetism, recognizes outstanding achievements in the fertilization of the earth sciences by the transfer and application of fundamental theory and/or experimental techniques of solid state physics.

Most recently, Dr. Parkin's focus has been on his latest invention, IBM Racetrack Memory, an entirely new way to store digital information that could lead to computer memory that combines the high performance and reliability of flash memory with the low cost and high capacity of the hard disk drive.

IBM's Racetrack Memory technology, so named because the data "races" around a nano-wire "track," is the latest evolution in the field of spintronics, which uses the spin, rather than the charge, of an electron to create electronic devices. Within the next 10 years, the technology could lead to solid state electronic devices - with no mechanical moving parts, which should therefore make it more durable - capable of holding far more data in the same amount of space than is possible today.

For example, this technology could enable a handheld device such as an MP3 player to store around 500,000 songs or around 3,500 movies - 100 times more than is possible today - in the same space with lower cost, lower power consumption and higher durability. The result: massive amounts of personal storage that could run on a single battery for weeks at a time and could possibly last for decades.

Digi-Key Corporation and Cooper Bussmann Expand Distribution Agreement
Electronic component distributor Digi-Key Corp., recognized by design engineers and purchasing professions as having the industry’s broadest selection of electronic components available for immediate shipment, has expanded its distribution agreement with Cooper Bussmann from a North American agreement to a global agreement.

Cooper Bussmann products offered by Digi-Key include Cooper Bussmann circuit protection fuses and ESD suppressors, Coiltronics inductors and transformers, and PowerStor supercapacitor lines. Stocked products are featured in Digi-Key’s print and online catalogs and are available in prototype/design and production quantities on Digi-Key’s global websites.

The US Magnet Cluster: Critical for the US Economy
By Ed Richardson, Marketing & Sales Manager • Thomas & Skinner, Inc.

The United States is on the threshold of a green revolution. The world is suddenly becoming more electric and less reliant on fossil fuels. This transition is underway and seemingly unstoppable as “green technologies” enter the marketplace with alarming speed. Nearly all of these alternative energy technologies focus on how to produce clean electrons. This focus is creating a tremendous amount of innovation and business opportunity, especially for the magnet industry.

Pushing the Strength of Motor Magnets
By Flemming Buus Bendixen and Anette Nørskov Schultz • Sintex a/s, Denmark

Magnetic design is often challenged by improvements in motor design and thus demands on higher density at preferably a smaller size. Utilizing the magnet properties and securing the magnet protection is essential in the magnetic design. This article will identify the strength of motor magnets, what areas might be improved and alternative solutions.

Magnetics 2010
January 28-29
Orlando, Fla.

This two-day conference is a leading global event within the magnetics market, bringing together worldwide magnetics experts. This is a once-a-year opportunity for professionals involved in magnetics technologies to learn the latest advancements in magnetic applications, technology and materials.

Magnetics 2010 will focus on the latest advancements in magnetic applications, technology and materials. Serving OEM developers of products that utilize magnets and magnet systems, design engineers, OEM developers involved in EMC technology and magnetic effects, magnetics manufacturers and integrators, and material suppliers in the magnetics industry.

Download a PDF Copy of the Summer 2009 Issue of Magnetics Business & Technology Magazine

ISSUE INCLUDES:

• Research & Development
• Feature Articles / Columns
• New Magnetics Products / Technology
• Industry News

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