Antiferromagnets for spintronics : exchange bias, spin dependent transport

Orateur : Soutenance d’HDR de Vincent BALTZ

The talk will be focused on two distinct aspects involving antiferromagnetic materials for spintronics devices : ferromagnetic / antiferromagnetic exchange bias and spin-dependent transport with antiferromagnets. The first part will be devoted to ferromagnetic / antiferromagnetic exchange bias. In particular, the exchange bias properties distributions in sheet films and from cell to cell in a magnetic random access memory chip result from the combination of several phenomena including the ferromagnetic / antiferromagnetic glassy character. Although interfacial spin-glasses have been for long known as an exchange bias key ingredient, few quantitative data were available since no versatile technique existed so far for their measurement : routinely available, fast and compatible with most bilayers. I will detail how, via the combination of an existing method and its simple extrapolation to low-temperatures, we quantified, at the laboratory level, the spin-glass character of ferromagnetic / antiferromagnetic bilayers with bimodal distributions of blocking temperature. Then, some of the insights that such a quantitative approach brought for applied spintronics will be shown. In the second part of this talk, future research topics will be introduced and especially the use of antiferromagnets for spin-dependent transport. A specific focus will be laid on one of the unsolved issues in antiferromagnets-based spintronics : the experimental determination of spin current penetration depths in antiferromagnets and the influence of the interfacial structure.

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