Deformation induced thermoremanent magnetisation in an FeMnNiCr antiferromagnetic alloy

▶ Thermoremanent magnetisation in FeMnNiCr due to cold deformation. ▶ Uncompensated antiferromagnetic moments appear and scale with the degree of deformation and are responsible for the thermoremanent magnetisation. ▶ Clusters of uncompensated moments act as superparamagnets coupling to the antiferr...

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Published in:Journal of alloys and compounds 2011-03, Vol.509 (9), p.3726-3734
Main Authors: Geissler, D., Müller, K.-H., Freudenberger, J., Nenkov, K., Krautz, M., Eickemeyer, J., Schultz, L.
Format: Article
Language:English
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Summary:▶ Thermoremanent magnetisation in FeMnNiCr due to cold deformation. ▶ Uncompensated antiferromagnetic moments appear and scale with the degree of deformation and are responsible for the thermoremanent magnetisation. ▶ Clusters of uncompensated moments act as superparamagnets coupling to the antiferromagnet by exchange anisotropy. In an austenitic Fe61.5Mn23Ni7Cr8.5 antiferromagnetic (afm) alloy deformation results in a splitting between magnetisation-vs.-temperature curves measured during field cooling (FC) below the Néel temperature and those measured at the same field after zero-field cooling (ZFC). Furthermore, a thermoremanent magnetisation (TRM) appears that corresponds to the splitting between zero-field and field cooled thermomagnetic measurements for a given cooling field and scales with the degree of deformation. This TRM is attributed to the deformation induced defects which act as a source of uncompensated magnetic moments and interact with the bulk afm moments. This interpretation is also supported by the fact that the net magnetic moments vanish above the Néel temperature. The TRM does not saturate in fields of up to 7T, applied during cooling, and cannot be switched by fields up to 7T. Within the investigated field range of −7T to 7T the magnetisation-vs.-field curves show a stable shift along the magnetisation axis. Thus, the uncompensated moments appear to be strongly exchange coupled to the afm matrix surrounding them. Within the series of experiments the maximum TRM reached after FC in 7T corresponds to about 4×10−4μB/atom (Bohr magneton) of the maximum deformed afm sample. The Néel temperature decreases due to deformation.
ISSN:0925-8388
1873-4669
DOI:10.1016/j.jallcom.2010.12.158