With a combinatorial strategy, scientists can look at many atom substitutions and ratio adjustments in a single combinatorial library. To look for new materials with magnetoresistance, the researchers began with a well-studied class of MR materials based on manganese oxide. The researchers found success with the cobalt oxide library, which yielded 26 new MR materials. Colossal MR materials lose a great deal of their resistance in magnetic fields, some as much as 99.99 percent. Although the phenomenon is still not well understood, scientists suspect magnetoresistance has to do with a physical characteristic known as spin polarization.
Spin polarization affects how electrons can be passed back and forth between neighboring atoms.
Atoms with similar spin polarizations are much more likely to transfer electrons between one another than those with different spin polarizations. It is thought that magnetism aligns the spin polarization in MR materials. This lets electrons jump more freely between atoms, causing resistance in a material to decrease. In the past, combinatorial approaches have been used successfully by researchers in the life sciences, who have searched for potential drugs by screening vast libraries of protein combinations. Xiang and Schultz are the first to apply the philosophy to solid-state materials.