??Inducing uniaxial magnetic anisotropy

Magnetic materials that have a preferred direction, i.e. a direction in which the magnetic moments are preferentially arranged, have magnetic anisotropy. In the case of magnetic thin films, the shape usually ensures that the magnetic moments are preferably oriented in the plane of the magnetic thin film. In addition to this so-called shape anisotropy, other anisotropies can also be present. An example is magnetic uniaxial anisotropy in the film plane. This ensures that the magnetic moments not only lie preferably in the film plane but are also oriented along a certain direction within the film plane. Such uniaxial anisotropies are relevant for various applications, such as magnetic tunnel contacts, which in turn are used in read heads of hard disk drives or in magnetoresistive RAM (MRAM).

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Uniaxial magnetic anisotropies can have various causes, but they can also be actively impressed into magnetic thin films. Two possibilities to be investigated in this work are the application of an external magnetic field during deposition and the use of a low angle of incidence of the atoms arriving at the substrate. The films are produced using magnetron sputter deposition and then examined for their magnetic properties using advanced magnetometry.

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Contact: If you are interested, please contact Stephan Glamsch.?→ @

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? Crystallization of orthoferrite thin films by post-annealing

Orthoferrites have interesting magnetic properties when prepared as a single crystal film. In single crystals, the atoms are arranged in a uniform, coherent lattice. However, when we deposit thin films of orthoferrite at room temperature, we obtain an amorphous material that is structurally disordered. However, such amorphous films can crystallize upon heating. In this work, amorphous orthoferrite films are grown by pulsed laser ablation and then brought into their crystalline form by post-annealing.

The post-tempering conditions (temperature, tempering time) should be varied and optimized. In addition, a so-called “rapid thermal annealing” system, which enables heating rates of up to 400 K/s, can also be used. The structural properties of the films treated in this way are analyzed by X-ray diffraction and scanning electron microscopy.

Contact: If you are interested, please contact Christian Holzmann.?→ @

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? Synthesis and characterization of highly entropic perovskites as bulk material

Highly entropic materials are materials that still crystallize in a single phase due to their high entropy. Entropy dominates here and ensures a minimization of the Gibbs free energy

G = H – TS.

We focus on high-entropy perovskites and investigate the influence of different materials on the magnetic properties. The aim of the work is to produce various high-entropy perovksites using a solid-state reaction. The materials are examined for their structural properties using X-ray diffraction and then examined their magnetic properties at low temperatures. The properties will then be compared with other high-entropy materials.

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Contact: If you are interested, please contact Maximilian Mihm.?→ @

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? Growth and characterization of epitaxial Co₃O₄ thin films

Co₃O₄ is a spinel (AB₂X₄) with a cubic lattice. It is also an antiferromagnet (in an antiferromagnet the magentic spins align antiparallel). This antiferrimagnetic material system is of particular interest as it may be suitable for spintron