Molecular hyperfine fields in organic magnetoresistance devices

Ronaldo Giro, Flávia P. Rosselli, Rafael dos Santos Carvalho, Rodrigo B. Capaz, Marco Cremona, and Carlos A. Achete
Phys. Rev. B 87, 125204 – Published 22 March 2013

Abstract

We calculate molecular hyperfine fields in organic magnetoresistance (OMAR) devices using ab initio calculations. To do so, we establish a protocol for the accurate determination of the average hyperfine field Bhf and apply it to selected molecular ions: NPB, TPD, and Alq3. Then, we make devices with precisely the same molecules and perform measurements of the OMAR effect, in order to address the role of hole-transport layer in the characteristic magnetic field B0 of OMAR. Contrary to common belief, we find that molecular hyperfine fields are not only caused by hydrogen nuclei. We also find that dipolar contributions to the hyperfine fields can be comparable to the Fermi contact contributions. However, such contributions are restricted to nuclei located in the same molecular ion as the charge carrier (intramolecular), as extramolecular contributions are negligible.

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  • Received 13 August 2012

DOI:https://doi.org/10.1103/PhysRevB.87.125204

©2013 American Physical Society

Authors & Affiliations

Ronaldo Giro1,*, Flávia P. Rosselli1, Rafael dos Santos Carvalho2, Rodrigo B. Capaz1,3, Marco Cremona1,2, and Carlos A. Achete1,4

  • 1Divisão de Metrologia de Materiais, Instituto Nacional de Metrologia, Qualidade e Tecnologia (INMETRO), CEP 25250-020, Duque de Caxias-RJ, Brazil
  • 2LOEM, Departamento de Física, Pontifícia Universidade Católica do Rio de Janeiro, PUC-Rio, CP 38071, CEP 22453-970, Rio de Janeiro-RJ, Brazil
  • 3Instituto de Física, Universidade Federal do Rio de Janeiro, Caixa Postal 68528, Brazil
  • 4Departamento de Engenheria Metalúrgica e de Materiais, Universidade Federal do Rio de Janeiro, CP 68505, CEP 21945-970, Rio de Janeiro-RJ, Brazil

  • *Author to whom correspondence should be addressed: rgiro@br.ibm.com—currently he is working at IBM Research Brazil.

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Issue

Vol. 87, Iss. 12 — 15 March 2013

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