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Modeling magnetotransport in inhomogeneous (Ge,Mn) films
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View: Figures


Image of FIG. 1.
FIG. 1.

(Color online) (a) TEM plane view along [001] of an 80 nm-thick Ge0.9Mn0.1 thin film grown on Ge(001) at 100 °C using molecular beam epitaxy. The columns’ diameter and density are 3 nm and 35 000 μm−2, respectively. (b) Discretization of the physical regions (Ge matrix and Mn-rich nanocolumns) using the finite element generation of the gmsh package (Ref. 37). The calculation box contains 15 nanocolumns randomly distributed in the Ge matrix and almost corresponds to a 25 nm × 25 nm square of the TEM image. The mesh has been made finer in the vicinity of the columns. Neumann boundary conditions were applied with a uniform normal current on the bottom edge (incoming) and top edge (outcoming) and a vanishing normal current on the lateral edges.

Image of FIG. 2.
FIG. 2.

(Color online) (a) Simulated temperature dependence of the saturation magnetization of nanocolumns using a simple Bloch law. The columns are superparamagnetic with a blocking temperature TB  = 0.1 × TC , in agreement with experimental data. (b) Magnetization curves for different temperatures; nanocolumns are assumed to be identical noninteracting single magnetic domains. Above TB , they are superparamagnetic, and their magnetization curves are simulated using Langevin functions.

Image of FIG. 3.
FIG. 3.

(Color online) Results of numerical simulations. (a),(c) Magnetoresistance and (b),(d) Hall angle as a function of the b value. a and t are set to 100 and 0.5, respectively. (e) The magnetoresistance and (f) the Hall angle as a function of temperature t for a = 100 and b = 1000. In (a), the inset shows the high field MR for b = 20 and b = −20.

Image of FIG. 4.
FIG. 4.

(Color online) The (a) MR and (b) Hall angle for broad ranges of a and b values. The temperature was set to t = 0.1, and the field to 5 T.

Image of FIG. 5.
FIG. 5.

(Color online) (a) The magnetization, (b) the magnetoresistance and Hall angle, and (c)–(f) maps of current density vectors and equipotential lines for four different applied fields: 0 T, 0.05 T, 0.2 T, and 2 T. The following parameters were used: a = 100, b = 1000, and t = 0.5. The color scale is related to the current intensity and is kept the same for all four magnetic fields.


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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Modeling magnetotransport in inhomogeneous (Ge,Mn) films