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MA: Fachverband Magnetismus
MA 7: Magnetic Semiconductors
MA 7.5: Talk
Monday, March 16, 2015, 12:30–12:45, EB 202
Magnetic coupling and formation energy of oxygen vacancies in ZnFe2O4 — •Martin Hoffmann1,2, Sanjeev K. Nayak1, Waheed Adeagbo1, Karen L. Salcedo Rodríguez3, Claudia E. Rodríguez Torres3, Wolfram Hergert1, and Arthur Ernst2,4 — 1Martin Luther University Halle-Wittenberg, Germany — 2Max Planck Institute for Microstructure Physics, Halle, Germany — 3National University of La Plata, Argentina — 4University Leipzig, Germany
Cation site inversion between regular and inverse spinel compositions and oxygen vacancy (VO) mediated ferromagnetic coupling between Fe spins constitute two major physical mechanisms for the observed ferrimagnetism in ZnFe2O4 (ZFO) [PRB 89, 104411 (2014)]. We will discuss our studies on the magnetic coupling between the Fe ions in ZFO with and without VO. The formation energy of defects is used to analyze the stability of VO in ZFO for the experimental growth conditions. The Néel temperature (TN) is determined from Monte Carlo (MC) simulations using the magnetic exchange interactions (Jij) obtained from first-principles method. The correlation energy is treated using GGA+U, where it is found that the Jij change almost linearly with increasing values of U.
For TN comparable to the experimental results, the first neighbor interaction was small and positive as concluded from former experiments. With those Jij, the estimated temperature-dependent saturation magnetization from the MC simulations is in good agreement with recent measurements.