Episode 9: Magnetic properties tunable in high-entropy oxides

Little research has been done on the magnetic properties of high-entropy oxides, a challenge taken up by Alannah Hallas at the University of British Columbia in Canada, interviewed by MRS Bulletin podcaster Laura Leay. Hallas’s research group began by choosing five elements that would be magnetic and combining them in oxide form, rendering a spinel structure for further experimentation. To understand how progressive substitution of the magnetic metal cations with non-magnetic gallium would affect the magnetic properties of the spinel, Hallas found that Ga substitution led to precise control of the configurational entropy, which may help to stabilize the spinel structure. Manganese, cobalt, and iron were redistributed throughout the structure whereas nickel and chromium were unaffected. Ga substitution led to the ability to tune the magnetic properties of the material in some unexpected ways that the research team calls “entropy engineering.” The ability to tune the properties may have applications for energy and data storage, for example, and could lead to more sustainable technologies. This work was published in a recent issue of the Journal of the American Chemical Society.