The research revealed an abrupt magnetic transition brought about by the slightest change in thickness of the layer. Materials with exceptional electronic and magnetic properties are of great importance for many apps. A particularly versatile class of materials are the ‘perovskite oxides’.
Twente University researchers have discovered a special effect relating to the magnetism of one of such perovskite-oxides; lanthanum-manganese-oxide. This material consists of stackings of LaMnO3 unit cells, quite comparable to stacking of LEGO but the building blocks are only 0.4nm in size.
The new discovery is that the magnetism in these layers is switched on abruptly when the number of LaMnO3 building blocks changes from 5 to 6. The scientists grew thin films of the oxide on a perfectly flat crystal of nonmagnetic SrTiO3, using a technique called pulsed laser deposition. By adding a 6th layer of LaMnO3, the material switches from antiferromagnetic (antiferromagnets produce no magnetic field) to ferromagnetic. Such an abrupt transition has never been seen before. Using a Scanning SQUID Microscope, an instrument that uses superconducting electronics to measure magnetic fields with exquisite sensitivity, a direct image of the change in magnetic properties was obtained.
The discovery of such a sharp critical thickness for ferromagnetism makes it possible to define magnetic structures on a nanoscale and implies very sensitive new functionality is present, in which a slight alteration or addition can alter the magnetic properties of the structure. The researchers expect this to be not only limited to adding new layers, but possibly also to other manipulations such as applying electric fields or adsorbing specific molecules. Further study will be conducted, aimed at the use of the effect in IT and sensors. http://www.utwente.nl/en/news/!/2015/8/186940/unusual-discovery-in-thin-film-magnetism
3D Visualization of the magnetic effect using Squid Scanning Microscopy. Credit: Image courtesy of University of Twente
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