Manufacturing Bits: Jan. 20

Batman chips
The demand for faster and higher-density storage has prompted researchers to look for ways to control the magnetic states of tiny magnets. Seeking to improve the magnetic recording speeds and spatial resolutions in structures, Radboud University and others attempted to switch the magnetization in microstructures by using a femtosecond laser pulse.

The laser light did not switch the structure homogeneously, but instead, it formed a pattern that resembled a bat, or the Batman logo.

The magnetic structure, sized five by five thousandth of a millimeter (micron) shows a substructure in black and white, reminding of the Batman logo. (Source: Radboud University)

To enable such as structure, researchers reported on the experimental demonstration of a sub-100 picosecond, all-optical magnetization switching technology in GdFeCo microstructures. This, in turn, could provide a path towards sub-wavelength magnetic recording.

On its Web site, Theo Rasing, a professor at Radboud University, said: “Since our group in Nijmegen discovered that femtosecond laser pulses are able to reverse magnetization, we started to work on how to minimize the size of the switched domain. You can in principle follow two approaches: make the structures smaller or focus the light to a smaller spot. By structuring the materials we discovered indeed that you can achieve sub-wavelength switching even on much larger structures. By controlling the laser pulse, this can be done in a controlled way. The ability to detect magnetic changes with sub-100 nm resolution was crucial for the whole project. Our collaborations through EU-networks with the main synchrotrons in Europe therefore played a decisive role for the success of this project.”

Measuring attoseconds
The Max Planck Institute of Quantum Optics, TU München and others have solved a major mystery in the electronics industry. Researchers measured how long electrons need to travel through single atomic layers.

The answer can be measured in mere attoseconds. An attosecond is one quintillionth of a second.

In the lab, researchers applied a defined number of layers of magnesium atoms on top of a tungsten crystal. Then, researchers used sub-femtosecond, extreme-ultraviolet light pulses to launch photoelectron wave packets inside the tungsten crystal.

A researcher at the attosecond beamline where the experiments were carried out. (Source: Thorsten Naeser)

The first pulse lasted about 450 attoseconds. This light pulse penetrated the material. This, in turn, released an electron from a magnesium atom and an atom in the tungsten crystal.

Then, the particles were captured by the electric field of the second pulse. “The measurements determined that a ‘tungsten electron’ is delayed when travelling through a layer of magnesium atoms by approximately 40 attoseconds, i.e., this is exactly the time required to travel through this layer,” according to researchers.

On its Web site, Reinhard Kienberger, a professor at the Max Planck Institute of Quantum Optics, said: “While a large number of electrons are able to cover increasingly large distances in today’s transistors, for example, individual electrons could transmit a signal through nanostructures in the future. As a result, electronic devices like computers could be made to be several times faster and smaller.”

Magnetic measurements
Helmholtz-Zentrum Berlin (HZB) and others have developed a new system that measures the 3D magnetic fields in sample materials.

The system, dubbed VEKMAG, is a vector superconducting magnet station. It consists of three perpendicular Helmholtz coils, which enables the measurement of a sample in the local magnetic field at any orientation in a vacuum chamber.

Here’s a graphic representation of the VEKMAG. The vector magnet chamber (grey) is supported by a hexapod frame. The detector chamber (green) is shown. In the forward direction, the deposition chamber (dark grey) is displayed. The beam quality is monitored by a diagnostic chamber (yellow). (Graphic: Dr. Tino Noll)

The system can be used to measure magnetic materials, spintronics devices and other structures. VEKMAG is designed for other measurements, such as XAS/XMCD as well as resonant and-off resonant soft X-ray scattering. The instrument can be used for time resolved ferromagnetic resonance using XMCD, in high magnetic fields and for a temperature range of < 2 K – 500 K.

The superconducting coils are made of a niobium-titanium alloy and cooled with liquid helium. The deposition chamber was designed at Freie Universität Berlin. Ruhr Universität Bochum built the detector chambers, and Universität Regensburg developed the concepts for synchrotron beam-based ferromagnetic resonance experiments.

“We need an extremely stable beam, but we also want to be able to change the polarization of the x-rays very rapidly,” said HZB physicist Florin Radu, on the research institute’s Web site. “For that reason, we developed a hexapod vacuum chamber with six moveable legs supporting a mirror. By changing the leg positions slightly, we can change the orientation of the first mirror and thereby the polarization of the x-ray beam in just seconds–about one hundred times faster than before.”