Strain-resistance effect of metallic sensor layers in the antiferromagnetic state

• Applicant: Professor Dr. Günter Schultes
• Subject Area: Synthesis and Properties of Functional Materials
• Term: from 2019 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 434934562

The aim of this proposal is to investigate a hardly known, quite high strain-resistance effect linked to the antiferromagnetic phase. For this purpose, metallic thin films, which can be used as sensor layers for mechanical quantities, such as pressure and force are deposited and investigated in detail. The piezoresistive effect and its coupling to the antiferromagnetic state (AFM) of metal layers made of chromium has been proven by our preliminary work. The proposed project is therefore based on chromium-containing layers which are now modified with low concentrations of elements such as Mn, Ru and others in order to shift the antiferro-paramagnetic transition temperature TNéel to higher values. The main properties are a high strain sensitivity, a low temperature coefficient (TKR), a high resistance stability and the highest possible application temperatures. The aim is to achieve the highest possible strain sensitivity, constant or slightly increasing over temperature, with low TKR and high stability. Then manganese-containing compounds with known high Néel temperatures are produced, which already play a role in the research of antiferromagnetic spintronics, but whose piezoresistive properties have not yet been investigated. These materials include binary compounds such as MnNi, MnPd, MnPt, MnIr and Mn2Au with extraordinarily high Néel temperatures of 810 K to 1500 K. Some of these compounds are deposited as thin films by sputtering, structured and investigated for their properties. In addition, the coatings are characterized by EDX, XPS, XRD and magnetic susceptibility measurements. Suitable layers are deposited as functional layers on pressure sensor bodies, structured as measuring bridges and then fully characterized and optimized with respect to their suitability as sensor layers. The research and optimization of metallic antiferromagnetic thin films with high strain sensitivities at high application temperatures promises an interesting application potential in sensor technology. In addition, the results can lead to findings that are also useful for the spintronics of antiferromagnetic layers.

• DFG Programme: Research Grants