Scientists hope that patterning magnetic materials with nanometer-scale structures will help the development of non-volatile electronic memories with large storage capacities and no moving parts. So-called magnetoresistive random access memories are one example. But material properties at such tiny dimensions are not always the same as those of larger structures.
The ‘in-plane’ ferromagnetic-resonance response of a magnetic nanostructure changes with device size —shown here in the simulation results by the rapidly varying colors. The ‘out-of-plane’ response, on the other hand, is relatively constant.
© 2014 A*STAR Data Storage Institute
Kwaku Eason, Maria Sabino and their co-workers from the A*STAR Data Storage Institute, A*STAR National Metrology Centre and National University of Singapore have now modeled the changes in the characteristics of magnetic materials as devices are reduced in size to the nanoscale1.
The researchers focused their attention on modeling a powerful and widespread tool for characterizing magnetic materials called ferromagnetic resonance (FMR). FMR measures the absorption of microwave radiation by a thin sample. Knowing which microwave frequencies are absorbed the most can provide a number of key material properties. One such crucial property is the damping parameter, which is an indicator of how quickly a memory made from the magnetic material can store and release data.
The team employed a mathematical tool, known as the finite element method, to simulate a simple cylindrical nanodevice in all three dimensions. By calculating the energy levels of the device in an external magnetic field, the team could predict the FMR signal for devices of varying sizes.
The researchers compared their simulations to experimental data obtained on nanodisks made of a nickel–iron alloy, known as permalloy, and found good agreement for all device sizes. “Other groups have provided additional experimental results that further confirm the accuracy of our predictions,” says Eason.
The ability to predict the damping parameter of nanostructured magnetic materials is important because it is difficult to experimentally measure this property — partly because FMR signals from tiny targets are usually weak. Instead, researchers must study much larger devices and hope that the damping parameter is similar for nanostructures.
Recent experiments have conflicted on this point of scale. “One research group found from their experiments that device size does not matter in the damping measurement, while another group found that it does,” explains Eason. “We have resolved this dilemma: it turns out that they were both right.” Sabino adds: “The results were contradictory because of the different material properties.”
The simulations showed that the ‘in-plane’ magnetic properties are sensitive to the dimensions of the device, whereas the ‘out-of-plane’ properties are constant (see image).
“Contributing to a clear understanding of this effect is one of the most gratifying parts of this work,” says Eason.
The A*STAR-affiliated researchers contributing to this research are from the Singapore-based Data Storage Institute and the National Metrology Centre
Eason, K., Sabino, M. P. R. G., Tran, M. & Liew, Y. F. Origins of magnetic damping measurement variations using ferromagnetic resonance for nano-sized devices. Applied Physics Letters 102, 232405 (2013).
UT professor develops algorithm to improve online mapping of disaster areas
29.11.2016 | University of Tennessee at Knoxville
New standard helps optical trackers follow moving objects precisely
23.11.2016 | National Institute of Standards and Technology (NIST)
A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.
Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...
In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.
“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...
The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.
The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...
Broadband rotational spectroscopy unravels structural reshaping of isolated molecules in the gas phase to accommodate water
In two recent publications in the Journal of Chemical Physics and in the Journal of Physical Chemistry Letters, researchers around Melanie Schnell from the Max...
The efficiency of power electronic systems is not solely dependent on electrical efficiency but also on weight, for example, in mobile systems. When the weight of relevant components and devices in airplanes, for instance, is reduced, fuel savings can be achieved and correspondingly greenhouse gas emissions decreased. New materials and components based on gallium nitride (GaN) can help to reduce weight and increase the efficiency. With these new materials, power electronic switches can be operated at higher switching frequency, resulting in higher power density and lower material costs.
Researchers at the Fraunhofer Institute for Solar Energy Systems ISE together with partners have investigated how these materials can be used to make power...
16.11.2016 | Event News
01.11.2016 | Event News
14.10.2016 | Event News
02.12.2016 | Medical Engineering
02.12.2016 | Agricultural and Forestry Science
02.12.2016 | Physics and Astronomy