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Tailoring of the structural and magnetic properties of MnAs films grown on GaAs—Strain and annealing effects
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10.1116/1.1978902
/content/avs/journal/jvstb/23/4/10.1116/1.1978902
http://aip.metastore.ingenta.com/content/avs/journal/jvstb/23/4/10.1116/1.1978902
View: Figures

Figures

Image of FIG. 1.
FIG. 1.

XMCDPEEM images of MnAs films on GaAs(001) representing two different thickness ranges. Mn edge . (a) Film thickness 37 nm, field of view (FOV) 5 μm, (b) film thickness 320 nm, FOV 10 μm. Both samples were annealed under flux at 400 °C for 10 min after MBE growth. The 37-nm-thick sample was additionally annealed without flux at 370 °C for 10 min before the XMCDPEEM measurement. The images were taken at after heating from below 0 °C. The films are in the multidomain state with the magnetic moment pointing along the (bright region) and antiparallel along the direction (dark region). There is strong ferromagnetic coupling across the paramagnetic stripes (grey) running along [0001] in the thin film (a), which is not observed in the thicker film (b).

Image of FIG. 2.
FIG. 2.

Thickness dependence of the saturation magnetization at RT for MnAs/GaAs(001) and MnAs/GaAs(111)B films. The data for the films on GaAs(001) refer to as-grown films and were corrected for the actual -phase content. The data for films on GaAs(111)B refer to films annealed at ELETTRA (without flux) during As decapping, and were not corrected for the actual -phase content. The 270-nm-thick film was additionally annealed without flux at 370 °C for 10 min before the XMCDPEEM measurement.

Image of FIG. 3.
FIG. 3.

Temperature dependence of (a) the saturation magnetization of a 108-nm-thick MnAs/GaAs(001) film measured without external field and (b) in a field of 1000 Oe (b), heating/cooling rate 1 K/min. The cooling and heating branches [lower and upper curve, respectively, in (a)] almost coincide when applying the field. The letters A, B, C, and D denote temperature regions with characteristic differences in the magnetic microstructure (cf. Fig. 4).

Image of FIG. 4.
FIG. 4.

Temperature-dependent magnetic structure of a 108-nm-thick MnAs/GaAs (001) film during heating from the completely ferromagnetic (a), (b) to the completely paramagnetic state (f), heating rate . In (c), (d), (e) the ferromagnetic phase and paramagnetic phase coexist. The ferromagnetic interaction between the -phase stripes decreases with increasing temperature. This explains the existence of characteristic temperature regions in the heating branch of curves (cf. Fig. 3). FOV 5 μm.

Image of FIG. 5.
FIG. 5.

Temperature dependence of the saturation magnetization of a 37-nm-thick MnAs/GaAs(001) film measured (a) without external field and (b) in a field of 1000 Oe. Heating/cooling rate 1 K/min. The letters A, B, and D denote temperature regions as described in the text. For the magnetic structure, see Fig. 1(a).

Image of FIG. 6.
FIG. 6.

Temperature dependence of the saturation magnetization of a 500-nm-thick MnAs/GaAs(001) film measured (a) without external field and (b) in a field of 2000 Oe (b), heating/cooling rate 1 K/min. XMCDPEEM images taken at 295 and 306 K are shown in (c) and (d), respectively. FOV 5 μm. The many regions with opposite magnetization in neighboring ferromagnetic stripes are the reason that the thermal hysteresis can not be lifted by applying the field.

Image of FIG. 7.
FIG. 7.

Magnetic hysteresis loops measured at RT for several film thicknesses. With increasing thickness the shape becomes more complex due to reduced ferromagnetic inter- and intra-stripe coupling [cf. insets in (a) and (c) and Figs. 1, 4, and 6]. The insets are XMCDPEEM images measured at RT after heating from below 0 °C. FOV 5 μm.

Image of FIG. 8.
FIG. 8.

(a) Magnetic hysteresis loops measured at RT of an as-grown and of an annealed 50-nm-thick MnAs/GaAs(001) film (a). Annealing under flux at 400 °C for 10 min. AFM images of (b) the as-grown and (c) the annealed film. The grey scale comprises 20 nm in (a) and 25 nm in (b).

Image of FIG. 9.
FIG. 9.

Cross-sectional SEM image of (a) the as-grown and As-capped MnAs/GaAs(001) film and (b) the film after decapping and an annealing without flux at 370 °C for 10 min. As a consequence of the annealing, the film thickness increases from 320 to 365 nm. In (b) a crack along (normal to the plane) is visible. The XMCDPEEM image taken at 315 K (c) reveals still clear ferromagnetic contrast near a crack (indicated by arrow), but not aside of it. FOV 5 μm.

Image of FIG. 10.
FIG. 10.

Magnetic hysteresis loops measured at RT for MnAs/GaAs(001) films which were annealed at 400 °C under flux after MBE growth, and additionally at 370 °C without flux at ELETTRA.

Image of FIG. 11.
FIG. 11.

XMCDPEEM images of a 270-nm-thick MnAs/GaAs(111)B film (annealed under flux at 300 °C for 5 min) taken at 293 K before applying a field (a) and taken at 280 K (b), 315 K (c), and 332 K (d) after applying a field along an easy axis. Heating rate . FOV 5 μm. In (a) magnetic domains in three equivalent orientations are imaged as black, white, and grey contrast. The coexisting phase (grey lines) forms a honeycomblike network. In (b) one of the -phase stripes along is highlighted by a white line.

Image of FIG. 12.
FIG. 12.

(a) Magnetic hysteresis loops measured at RT for MnAs/GaAs(111)B films with different thickness. (b) Typical curve of a 270-nm-thick film (annealed under flux at 300 °C for 5 min) measured in zero field and (c) curves measured in a field of 1000 Oe for films of different thickness. Heating/cooling rate 2 K/min.

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/content/avs/journal/jvstb/23/4/10.1116/1.1978902
2005-07-25
2014-04-21
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Tailoring of the structural and magnetic properties of MnAs films grown on GaAs—Strain and annealing effects
http://aip.metastore.ingenta.com/content/avs/journal/jvstb/23/4/10.1116/1.1978902
10.1116/1.1978902
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