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arXiv · 2101.03900

Strain Induced Anisotropic Magnetic Behaviour and Exchange Coupling Effect in Fe-SmCo$_{5}$ Permanent Magnets Generated by High Pressure Torsion

Lukas Weissitsch·Martin Stückler·Stefan Wurster·Peter Knoll·Heinz Krenn·Reinhard Pippan·Andrea Bachmaier
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Abstract

High-pressure torsion (HPT), a technique of severe plastic deformation (SPD), is shown as a promising processing method for exchange-spring magnetic materials in bulk form. Powder mixtures of Fe and SmCo$_{5}$ are consolidated and deformed by HPT exhibiting sample dimensions of several millimetres, being essential for bulky magnetic applications. The structural evolution during HPT deformation of Fe-SmCo$_{5}$ compounds at room- and elevated- temperatures of chemical compositions consisting of 87, 47, 24 and 10 wt.% Fe is studied and microstructurally analysed. Electron microscopy and synchrotron X-ray diffraction reveal a dual-phase nanostructured composite for the as-deformed samples with grain refinement after HPT deformation. SQUID magnetometry measurements show hysteresis curves of an exchange coupled nanocomposite at room temperature, while for low temperatures a decoupling of Fe and SmCo$_{5}$ is observed. Furthermore, exchange interactions between the hard- and soft-magnetic phase can explain a shift of the hysteresis curve. Strong emphasis is devoted to the correlation between the magnetic properties and the evolving nano-structure during HPT deformation, which is conducted for a 1:1 composition ratio of Fe to SmCo$_{5}$. SQUID magnetometry measurements show an increasing saturation magnetisation for increasing strain $γ$ and a maximum of the coercive field strength at a shear strain of $γ$ = 75.

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Lukas Weissitsch, Martin Stückler, Stefan Wurster, Peter Knoll, Heinz Krenn, Reinhard Pippan, Andrea Bachmaier. 2021-01-19. Strain Induced Anisotropic Magnetic Behaviour and Exchange Coupling Effect in Fe-SmCo$_{5}$ Permanent Magnets Generated by High Pressure Torsion. https://doi.org/10.3390/cryst10111026

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