Contact

Fecher, Gerhard
Gerhard Fecher
Senior Chief Research Officer
Phone: +49 351 4646-2240
Fax: +49 351 4646-3002

Physics, Electronic structure

Publication highlights

1.
C. E. ViolBarbosa, S. Ouardi, T. Kubota, S. Mizukami, G. H. Fecher, T. Miyazaki, X. Kozina, E. Ikenaga, and C. Felser, "Investigation of the Mn3-δ Ga/MgO interface for magnetic tunneling junctions," Journal of Applied Physics 116 (3), 1-4 (2014).
2.
Carlos E. ViolBarbosa, Siham Ouardi, Takahide Kubota, Shigemi Mizukami, Gerhard H. Fecher, Terunobu Miyazaki, Eiji Ikenaga, and Claudia Felser, "Forward scattering in hard X-ray photoelectron spectroscopy: Structural investigation of buried Mn-Ga films," Applied Physics Letters 106 (5), 1-5 (2015).

Heusler-based magneto tunneling junction

 

Improving interfaces

The Mn3Ga Heusler compound and related alloys are promising materials for the realization of spin-transfer-torque magnetoresistive memories. For this propose is essential to master the growth process of Mn-Ga films in multilayered structures. HAXPES is able to chemically characterize these structures probing buried interfaces. We investigated the MgO/Mn-Ga junction by HAXPES and found the formation of gallium oxides at the interface. We show that the deposition of few monoatomic layers of Mg on top of Mn–Ga film, before the MgO deposition, strongly suppresses the oxidation of gallium, improving the interface quality [1].

<div style="text-align: justify;"><strong>Figure 1:</strong> <em>Evidence of oxides in the MgO/Mn-Ga interface. The oxide is suppressed by a thin layer of Mg.</em></div> Zoom Image
Figure 1: Evidence of oxides in the MgO/Mn-Ga interface. The oxide is suppressed by a thin layer of Mg.

Structural information of Heulser films in multilayer structures

For high performance tunneling magneto junction, the crystal ordering of multilayered films is a crucial parameter. In Heusler compounds, the chemically disorder has strong impact in the electronic properties. Angular-resolved HAXPES can be used for structural investigation of a complex multilayer system. Since HAXPES is is an element-specific method, it is also suitable to study chemically disorder, providing complementary information to regular X-ray diffraction studies. The angular distribution of the photoemission of Mn-Ga films which is used to understand the chemical disorder in this material [2].

<p style="text-align: justify;"><strong>Figure 2:</strong> <em>Relation between the angular distribution of photoemission and internuclear axis of the tetragonal Mn-Ga film.</em></p> Zoom Image

Figure 2: Relation between the angular distribution of photoemission and internuclear axis of the tetragonal Mn-Ga film.

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