Going with the grain:
to a new superconducting material
Superconductors are powerful materials that conduct electricity with no resistance, meaning no loss of electricity. Recently, scientists have discovered a new class of superconducting materials called pnictides, which are based on iron and arsenide. Pnictides are promising because they can operate at relatively high temperatures and have other ideal properties.
A team led by Materials Science and Engineering Professor Chang-Beom Eom has demonstrated a breakthrough approach in fabricating pnictide thin films with promising results. Until now, no one has been able to study the intrinsic properties of pnictides because it has been impossible to fabricate a single crystal of it with all of the material grains pointing in the same direction.
Eom, who is collaborating with teams from the National High Magnetic Field Laboratory and the University of Michigan, hypothesized that the pnictide thin films couldn’t grow properly because the substrate used most commonly by researchers is oxide-based. Thin films like to grow in the same way as the material beneath them. Hence, the metallic-based pnictides couldn’t thrive on the oxide substrate.
The researchers then engineered a thin template to place on top of the oxide substrate. This template has both metallic and oxide elements, meaning it can interface with both the substrate and the thin film. With the template, the film grows in a more ideal arrangement. The template also acts as barrier between the conducting thin film and the non-conducting substrate.
Previously, researchers were only able to measure 10,000 amps of electricity per .06 cubic inch, which is a relatively useless amount. With the template, which is made of barium titanate or strontium titanate, Eom’s team has demonstrated that pnictide thin films are capable of producing 5 million amps per .06 cubic inch — a 500-fold increase that brings pnictide current capacity into the usable range.
The team’s research will help other researchers learn more about pnictides and expand basic knowledge about superconductivity in general. Beyond superconductors, the template approach can be applied whenever a researcher wants to grow a metallic film on an oxide substrate.
The research appeared online in the journal Nature Materials on February 28, along with a second paper by Eom about a new approach to help researchers “couple” the electric and magnetic mechanisms in a special class of materials. This could lead to a wide range of magnetoelectric devices, such as new integrated circuits or tiny electronic devices with the information storage capacity of hard drives.