Project Details
Projekt
Amorphous ferrimagnets as a platform for antiferromagnetic-like DMI skyrmions
Applicants
Professor Dr. Felix Büttner; Dr. Florin Radu
Subject Area
Experimental Condensed Matter Physics
Term
since 2021
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 462676630
Most magnetic skyrmions can be classified into two types. The first type is stabilized primarily by the Dzyaloshinskii-Moriya interaction (DMI) and the second is stabilized by stray-field interactions. These two types have never been observed in the same material and therefore little is known about possible differences in their physical properties. Here, we propose to establish the first materials system in which both types of skyrmions can be stable, and to directly image the transition from one type to the other. Our work builds on the recent discovery of bulk-like DMI in amorphous rare-earth transition-metal (RE-TM) ferrimagnets, based on which we predict a large phase pocket for sub-10 nm DMI skyrmions near the magnetic compensation points of films of several tens of nanometer in thickness. In the same films, we expect the formation of stray-field skyrmions at temperatures far away from compensation, as frequently reported in the literature. By finding the predicted DMI skyrmion phase pocket, we therefore anticipate gaining a powerful knob to continuously change between the preferred environments of DMI and stray-field skyrmions. Along this path, we expect to observe a transition from one type to the other, and by searching for signatures of a hysteresis we aim to determine if this transition is first-order-like or second-order-like. To facilitate this experiment, we will start with an extensive systematic explororation the materials parameter space of chiral amorphous RE-TM ferrimagnets. We will map out the dependence of all relevant micromagnetic parameters (sublattice magnetic moments, anisotropy constants, exchange constant, and DMI) as a function of composition, constituent elements, temperature, and film thickness. Combined with our analytical model for magnetic skyrmions, our results will produce a skyrmion materials selection guide with which one can define desired skyrmion properties and obtain a set of materials in which such properties can be realized. In addition, we will develop and demonstrate synchrotron-based techniques to accurately measure the profile and the chirality of the resulting solitonic magnetic textures in RE-TM ferrimagnets, without being restricted to the surface-near regions. Combined, this project will verify the theoretically predicted classification of skyrmions into DMI and stray-field types, provide the community with a skyrmion materials platform to systematically explore their physics, and open a path to utilize the transition (and possible the bi-stability) of these skyrmions in functional devices.
DFG Programme
Priority Programmes
