October 24, 2011 — A highly engineered lanthanum and strontium compound material could form the basis of spintronics devices, report Argonne National Laboratory (ANL) and the National Institute of Standards and Technology (NIST) researchers.

ANL team members engineered the highly ordered magnetic oxide compound of lanthanum and strontium. ANL used atomic layer deposition to organize the lattice in layers of just strontium and just lanthanum. In randomly created compounds, stronger magnetic properties are found where extra lanthanum atoms are added to the lattice. The researchers’ virtually perfect sample of the material allowed them to study fundamental characteristics, said Brian Kirby, a physicist at the NIST Center for Neutron Research (NCNR).

Figure. Manganite oxide lattices (blue) doped with lanthanum (red) and strontium (green) have potential for use in spintronic memory devices, but their usual disorderly arrangement (left) makes it difficult to explore their properties. The ANL/NIST team’s use of a novel orderly lattice (right) allowed them to measure some of the material’s fundamental characteristics. SOURCE: Argonne National Laboratory.

The NIST team members used the NCNR’s polarized neutron reflectometer to analyze the magnetic properties within this oxide lattice versus those of a random compound. The influence of electrons near the additional lanthanum layers was spread out across three magnetic layers in either direction, but fell off sharply further away than that. Tiffany Santos, lead scientist on the study from ANL, says that the measurement will be important for the emerging field of oxide spintronics, as it reveals a fundamental size unit for electronic and magnetic effects in memory devices made from the material.

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Referring to use for memory chips, Kirby says that electrons will need to be physically close enough to influence each other to share spin information. The precisely constructed compound showed the researchers "how big that range of influence is," Kirby explained.

Results were published in Physical Review Letters: T. S. Santos, B. J. Kirby, S. Kumar, S. J. May, J. A. Borchers, B. B. Maranville, J. Zarestky, S. G. E. te Velthuis, J. van den Brink and A. Bhattacharya. Delta doping of ferromagnetism in antiferromagnetic manganite superlattices. Physical Review Letters, Week ending Oct. 14, 2011, 107, 167202 (2011), DOI: 10.1103/PhysRevLett.107.167202.

The National Institute of Standards and Technology (NIST) is an agency of the U.S. Department of Commerce. Learn more at www.nist.gov.