‘Sandwich’ Structure Key to Thin LSMO Films Retaining Magnetic Properties
June 27, 2019 | NC State UniversityEstimated reading time: 2 minutes
Researchers at North Carolina State University have found that the oxide ceramic material lanthanum strontium manganite (LSMO) retains its magnetic properties in atomically thin layers if it is “sandwiched” between two layers of a different ceramic oxide, lanthanum strontium chromium oxide (LSCO). The findings have implications for future use of LSMO in spintronic-based computing and storage devices.
In its bulk form LSMO has both magnetic and metallic properties. The conductivity of the material can be altered by changing its magnetic field, which makes LSMO appealing for use as a switch in spintronic devices. However, when the material gets to a certain thinness — between five and 10 atomic layers — it loses these properties.
Divine Kumah, assistant professor of physics at NC State and corresponding author of a paper describing the work, wanted to know why LSMO loses its magnetic properties at a particular thinness, and to find a way to make LSMO magnetic in thin form.
Kumah, with colleagues and graduate students from NC State, first grew thin films of LSMO on strontium titanate — a non-magnetic substrate commonly used as a neutral scaffold. The team grew films ranging from two to 10 atomic layers thick and tested them for magnetic properties.
Next, the team utilized the synchrotron light source at Argonne National Laboratory so that they could get a three-dimensional view of the arrangement of the atoms within the thin layers of LSMO. They found that at extreme thinness, the oxygen and manganese atoms moved slightly out of alignment on the surface of the material, effectively switching off its magnetism.
“At about five atomic layers we saw distortions on the surface of the layer and at the bottom interface with the scaffold,” Kumah says. “The oxygen and manganese atoms rearrange themselves. Magnetism and electrical conductivity in LSMO are related to how these two atoms bond, so if there are polar distortions in the film where they move up and down, the bonds stretch out, electrons can’t move through the material effectively and magnetism is switched off.”
The team noted that these distortions started at the top of the film and extended approximately three layers below surface.
“We found that the distortions occur because the crystal structure creates an electric field at the surface,” Kumah says. “The oxygen and manganese atoms move in order to cancel the electric field. Our challenge was to grow something at the interfaces that is compatible with LSMO structurally but that is also insulating — so that we remove the electric field, stop the movement of the oxygen and manganese atoms and retain magnetic properties.”
The researchers found that by using two layers of LSCO on either side of the LSMO, the LSMO could retain its magnetic properties at two atomic layers.
“It is like a sandwich — LSCO is the bread and LSMO is the meat,” Kumah says. “You can use fewer than five layers of LSMO in this arrangement without any atomic displacement. Hopefully our work has shown that these materials can be thin enough to be useful in spintronics devices.”
Suggested Items
Groundbreaking Ceremony Marks the Beginning of a New Era for Newccess Industrial; The Construction of the MINGXIN Building
04/12/2024 | Newccess IndustrialOn a clear and sunny day in March, the groundbreaking ceremony for the MINGXIN Building took place in Shenzhen, China. This moment marked the official commencement of construction for a project that will reshape the semiconductor materials industry.
The Need for a Holistic Global Sustainability Standard
04/10/2024 | Michael Ford, Aegis SoftwareNo one can deny that the resources of our fragile planet are finite. The environment seems like a third party, subject to constant degradation. We’re acutely aware of the effects of pollution on our climate, and despite our “throw-away” culture, recycling and recovery of materials has remained relatively expensive, even as we use more energy just to survive.
Altus Group Celebrates 30 Years of Innovation with Scienscope
04/08/2024 | Altus GroupAltus Group, a prominent distributor of capital equipment within the electronics industry across the UK and Ireland, is pleased to commemorate the 30th anniversary of Scienscope International, a leading supplier of advanced inspection solutions.
iNEMI Publishes Four Roadmap Topics
04/04/2024 | iNEMIThe International Electronics Manufacturing Initiative (iNEMI) announces the availability of the first roadmap topics in the new iNEMI Roadmap format. Printed circuit boards, sustainable electronics, smart manufacturing, and mmWave materials and test are now available online.
Insulectro’s 'Storekeepers' Extend Their Welcome to Technology Village at IPC APEX EXPO
04/03/2024 | InsulectroInsulectro, the largest distributor of materials for use in the manufacture of PCBs and printed electronics, welcomes attendees to its TECHNOLOGY VILLAGE during this year’s IPC APEX EXPO at the Anaheim Convention Center, April 9-11, 2024.