Optimization of Heusler compounds for spintronics by control of the relation between structure and properties

Emmy Noether research group

The aim of this project in the frame work of an Emmy Noether group is to bring Heusler compounds towards spintronics.


A key tool in the rational design of spin polarised materials is the precise control of the relationships between
structure and physical properties, such as between structure and magnetism or transport properties. Thus, a
sophisticated and comprehensive characterisation is required in order to understand, tune and control the
macroscopic properties of spin polarised materials towards optimised performance in spintronic devices. My project
enables comprehensive studies of spin polarised materials such as Heusler compounds in a new way. The approach is threefold: First,
high quality single crystals will be grown as model systems. Second, their (local) structure will be studied by
Nuclear Magnetic Resonance (NMR) and third, the physical properties such as transport
behaviour, magnetism and thermodynamics will be studied and related to the structure. The investigation of
high quality single crystals offers the advantage of very reproducible and optimised characteristics without
any contributions from grain boundaries, thus revealing the intrinsic, generic properties of potential
materials. The method of choice for the preparation of Heusler single crystals is the floating zone technique,
for which the IFW has a well renowned expertise. The Heusler compounds are known to exhibit different
structure types, which will affect their performance in spintronic devices, leading to the requirement of a
thorough structural characterisation. In order to control the relationships between structure and physical
properties such as transport behaviour, magnetism and the thermodynamics of selected model systems and
devices, we will characterise their local structure by means of NMR. The combination of the investigation
methods to study (single) crystalline samples of spin polarised is quite unique and will lead to an iterative
optimisation of the sample quality. The investigation of the physical properties of the obtained high quality
model systems will yield valuable information about the intrinsic properties of Heusler compounds. The
knowledge and control of the intrinsic material properties are essential for properly rationalising the potential
of a particular material for spintronic applications. My approach will enhance the performance of Heusler compounds
in spintronic devices and bring them towards technical application. In the future, the iterative concept of optimising
the relations between the structure and the physical properties will be carried over also to other research fields
on Heusler compounds (e.g. spin caloritronics, thermoelectrica) and other classes of materials (e.g. intermetallic
or oxidic materials such as double perovskites).