Berlin 2015 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 7: Magnetic Semiconductors

MA 7.5: Vortrag

Montag, 16. März 2015, 12:30–12:45, EB 202

Magnetic coupling and formation energy of oxygen vacancies in ZnFe₂O₄ — •Martin Hoffmann^1,2, Sanjeev K. Nayak¹, Waheed Adeagbo¹, Karen L. Salcedo Rodríguez³, Claudia E. Rodríguez Torres³, Wolfram Hergert¹, and Arthur Ernst^2,4 — 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 (V_O) 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 V_O. The formation energy of defects is used to analyze the stability of V_O in ZFO for the experimental growth conditions. The Néel temperature (T_N) is determined from Monte Carlo (MC) simulations using the magnetic exchange interactions (J_ij) obtained from first-principles method. The correlation energy is treated using GGA+U, where it is found that the J_ij change almost linearly with increasing values of U.

For T_N comparable to the experimental results, the first neighbor interaction was small and positive as concluded from former experiments. With those J_ij, the estimated temperature-dependent saturation magnetization from the MC simulations is in good agreement with recent measurements.