Old rules apply in explaining extremely large magnetoresistance

Researchers in condensed matter physics at Ames Laboratory had recently discovered an extremely large magnetoresistance and a Dirac-node-arc feature in PtSn₄. In this work, the researchers found another material, PdSn₄, showing extremely large magnetoresistance but a gapped out Dirac-node-arc feature. In comparing these similar compounds, they ruled out Dirac-node-arc feature and electron-hole compensation as the mechanism to explain extremely large magnetoresistance.

They did find, however, that both materials' behaviors adhered to something called Kohler's Rule.

"There's this old empirical statement that if you make a metal cleaner and cleaner and cleaner, it results in larger and larger magnetoresistance," said Paul Canfield, a senior scientist at Ames Laboratory and a Distinguished Professor and the Robert Allen Wright Professor of Physics and Astronomy at Iowa State University. "Our results were an extreme example of what has been appreciated in metals physics for decades, but is now being observed at 100 or 1000 times greater extremes than we've seen before."

The comparative study serves to point the way to the conditions necessary to achieve extreme magnetoresistance.

"As a process of elimination, this work becomes a guide for future research," said Na Hyun Jo, a graduate assistant and co-author of the published research "Kohler's Rule explains the data, but it doesn't tell us why the magnetoresistance is so huge. But now we know that it is not because of Dirac node arcs, and not because of near compensation."