Spin valve (SV) devices are composed by two magnetic (FM) regions separated by a nonmagnetic region: one of two FM film is magnetically "soft" (free layer), and the other behaves as a magnetic "hard" layer (pinned layer) thanks to the exchange coupling (EC) with an adjacent antiferromagnetic (AFM) layer. The orientation of the magnetization of the FM soft "free" layer may change with respect to that of the pinned layer due to external applied fields, and the resistance of the whole system will vary due to its giant magnetoresistive (GMR) properties. The same effect may appear if the free layer has magnetostrictive properties and the system undergoes mechanical strain. Namely, it is possible to couple the strain state of the device to its electrical state, through the magnetic state and GMR properties. Moreover, thanks to spin-dependent conductivity, the SV strain gauge sensitivity is higher with respect to those based on conventional magnetoresistance. In this contribution, we address two main aspects of the SV system, the exchange bias phenomenon at the AFM/FM interface and the magnetostrictive properties of thin FM films. We use Fe50Mn50 as AFM layer and Fe50Co50, due to its magnetostrictive properties, as FM layer and we grow them on Kapton substrates via dc-magnetron sputtering in Ar atmosphere. On the one hand, we analyze the features that affect the intensity of the exchange bias at the interface between the two layers, in particular we present the effect of the thickness of the AFM layer, of its growth rate and of the Ar pressure during growth on the EC intensity. On the other hand, we show magnetostrictive measurements performed on thin FM films. Preliminary measurements of resistivity as a function on strain on the Fe50Mn50/Fe50Co50/Cu/Fe50Co50 SV system will be presented, as well.

AF/FM exchange bias in a magnetostrictive system

SPIZZO, Federico;TAMISARI, Melissa;DEL BIANCO, Lucia;RONCONI, Franco
2010

Abstract

Spin valve (SV) devices are composed by two magnetic (FM) regions separated by a nonmagnetic region: one of two FM film is magnetically "soft" (free layer), and the other behaves as a magnetic "hard" layer (pinned layer) thanks to the exchange coupling (EC) with an adjacent antiferromagnetic (AFM) layer. The orientation of the magnetization of the FM soft "free" layer may change with respect to that of the pinned layer due to external applied fields, and the resistance of the whole system will vary due to its giant magnetoresistive (GMR) properties. The same effect may appear if the free layer has magnetostrictive properties and the system undergoes mechanical strain. Namely, it is possible to couple the strain state of the device to its electrical state, through the magnetic state and GMR properties. Moreover, thanks to spin-dependent conductivity, the SV strain gauge sensitivity is higher with respect to those based on conventional magnetoresistance. In this contribution, we address two main aspects of the SV system, the exchange bias phenomenon at the AFM/FM interface and the magnetostrictive properties of thin FM films. We use Fe50Mn50 as AFM layer and Fe50Co50, due to its magnetostrictive properties, as FM layer and we grow them on Kapton substrates via dc-magnetron sputtering in Ar atmosphere. On the one hand, we analyze the features that affect the intensity of the exchange bias at the interface between the two layers, in particular we present the effect of the thickness of the AFM layer, of its growth rate and of the Ar pressure during growth on the EC intensity. On the other hand, we show magnetostrictive measurements performed on thin FM films. Preliminary measurements of resistivity as a function on strain on the Fe50Mn50/Fe50Co50/Cu/Fe50Co50 SV system will be presented, as well.
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11392/1433112
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