Tunneling Junctions

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].

Figure 1: Evidence of oxides in the MgO/Mn-Ga interface. The oxide is suppressed by a thin layer of Mg.

Structural information of Heusler 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].

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

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