Physical properties of magnetic materials produced by SPD

Project coordinator: Univ.Prof.Dr. R. Grössinger (Vienna University of Technology)

Within the present project the magnetic properties (hysteresis, magnetic viscosity, magnetostriction) of various kinds of magnetic materials [hard- & soft- magnetic, magnetostrictive materials and MSM (Magnetic Shape Memory Alloys)] will be investigated. The samples are produced by SPD (Severe Plastic Deformation, project 02, Pippan) or IGC (Inert Gas Condensation, project 05, Würschum) or by other methods in order to achieve a nanocrystalline state. SPD is a feasible method to produce new compositions and/or materials in a metastable state. At our "Institute of Solid State Physics" at TU Vienna and especially within the group for magnetism exists a long time experience on producing, characterising and measuring magnetic, especially nanocrystalline, materials.
Post-processing by SPD of conventional soft magnetic materials (such as Finemet-type or related compounds) is expected to influence substantially their hysteresis properties. The nanocrystalline state shall lead to a high permeability combined with a low coercivity. Hard magnetic materials (nanocomposites based on Nd2Fe14B or SmCo5 or Sm2Co17 + soft magnetic phase) produced by SPD will be investigated with respect to a possible remanence enhancement. High-magnetostrictive materials (as e.g. TbFe2 or SmFe2) in a nanocrystalline state are interesting because the reduced "effective" anisotropy facilitates the magnetization reversal, which is technically important. Measurements of the magnetic properties including magnetostriction measurements are necessary to determine the applicability of these materials. Also magnetic shape memory alloys (MSM) as well as magnetocaloric materials in a nanocrystalline state will be produced by SPD. Here especially the effect of SPD nanocrystallization on the martensitic transition is of interest (cooperation with project 03, Zehetbauer). All magnetic investigations will be accompanied within the NFN by determination of the microstructure (project 03, Zehetbauer, and project 04, Würschum) which is essential for understanding the magnetic behaviour. The magnetization process of these new nanocrystalline materials will be investigated in close cooperation with external partners: Prof. Hauser (T.U. Vienna), Prof. Bertotti (Torino) and Prof. Jiles (Univ. Cardiff) and by micromagnetic modelling (Preisach-, Jiles-models etc). The spectral analysis of the Barkhausen noise proposed by the group 07 (Krenn) adds interesting aspects for the dynamic study of the magnetization process.