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Séminaire NANO

Mardi 27 janvier à 9h30,
Salle Remy Lemaire, K223

Orateur : Dominique Givord (Nano MNM et UF Rio de Janeiro)
"Mn2Au, a new antiferromagnetic material, exchange-bias and possible spintronics applications "


Mn2Au, known as a Pauli paramagnet, is actually an antiferromagnet, with an extrapolated Néel temperature, TN, around 1450 K (the Mn2Au phase decomposes at 953 K). The Mn moments are confined in the basal plane of the tetragonal structure, with weak associated basal plane anisotropy. A neutron diffraction study under magnetic field indicates that the easy magnetization direction is [100]. AFM/FM Mn2Au/FeCo bilayers were prepared by magnetron sputtering. Large exchange-bias effects are observed at low temperature. The bias field decreases rapidly with temperature and vanishes around 100 K. A model to describe exchange-bias will be proposed which explains that reversal is fundamentally different whereas the field is swept from an initial value having the sign of the field applied during cooling or having the opposite sign. This model provides semi-quantitative account for the magnetization behaviour, which constitutes an original result for an exchange-bias system. The possible use of Mn2Au for antiferromagnetic spintronics will be briefly presented

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