Exploiting Synergies between Thin Films and Bulk Materials: the Key to Understanding Magnetic Properties and Magneto-Transport in MnAl

• Applicants: Privatdozent Dr. Andy Thomas, since 11/2020; Dr. Thomas G. Woodcock
• Subject Area: Synthesis and Properties of Functional Materials ; Experimental Condensed Matter Physics
• Term: from 2017 to 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 380033763

Magnetic materials with high magneotcrystalline anisotropy are required in both thin film and bulk forms for a wide spectrum of applications including emergent spintronic devices, computer storage media, motors for hybrid vehicles and generators for wind turbines. In addition to a high magnetocrstalline anisotropy, MnAl has recently been shown to exhibit novel magneto-transport effects. These aspects, combined with the fact that the material contains no rare earth elements and has low raw materials costs, make MnAl highly attractive for the applications mentioned above. The MnAl materials produced to date typically exhibit excellent values of some but not all the required magnetic properties. For example in thin films of MnAl, high coercivity with low saturation magnetisation has been reported, both of which are required in spintronic devices, but little is known about the (anisotropic) magnetoresistance. In bulk materials, high values of saturation magnetisation have been reported but the coercivity is significantly lower than that reported in thin films. High coercivity and magnetisation are crucial for permanent magnets. As the microstructure of MnAl thin films has not been studied and details of the microstructure in bulk MnAl are still emerging, the mechanisms leading to the contrasting magnetic properties in different forms of this material are not understood. The influence of some doping elements on the magnetic properties of bulk MnAl has been tentatively explored but much further work is required to clarify the effects. Very few studies have been carried out on doped MnAl films. Solving these problems is the key step which will allow the production of MnAl materials with magnetic properties tailored to applications in spintronics and permanent magnets.The development of thin films and bulk materials often takes place separately but in this project, synergies between thin films and bulk materials will be exploited in order to progress rapidly in understanding the magnetic properties and the effect of doping in MnAl. For example, by analysing highly coercive MnAl thin films and comparing their microstructure with that of MnAl bulk materials, the conditions necessary for high coercivity will be elucidated. Novel processing routes will be developed which reproduce these conditions in bulk materials. The solubility of the doping elements and phase equilibria will be studied in bulk materials, using the advantage that, unlike in thin films, no substrate is present which could influence the results. The knowledge gained from bulk will be transferred in order to accelerate the successful fabrication of doped films. The magnetic and magneto-transport properties of the materials produced will be studied in detail in order to elucidate the controlling mechanisms and assess their suitability for application.

• DFG Programme: Research Grants
• Ehemaliger Antragsteller: Professor Dr. Sebastian Gönnenwein, until 11/2020