Influence of ion bombardment on transport properties and exchange bias in magnetic tunnel junctions

Schmalhorst, Jan-Michael; Höink, V.; Reiss, Günter; Engel, Dieter; Junk, D.; Schindler, Axel; Ehresmann, A.; Schmoranzer, H.

doi:10.1063/1.1614846

Cited by 25 publications

(21 citation statements)

References 7 publications

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“…The ion beam induced modification of the exchange coupling across an antiferromagnetic/ferromagnetic interface is widely investigated for exchange bias systems for spin-valves [47][48][49][50][51] and for magnetic tunnel junctions [52,53]. In all these cases the magnitude of the exchange bias effect is directly related to the exchange coupling across the mutual interface between the ferromagnet and the antiferromagnet.…”

Section: Modification Of Exchange Couplingmentioning

confidence: 99%

Magnetic patterning by means of ion irradiation and implantation

Faßbender¹,

McCord²

2008

Journal of Magnetism and Magnetic Materials

233

134

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Section: Modification Of Exchange Couplingmentioning

confidence: 99%

Magnetic patterning by means of ion irradiation and implantation

Faßbender¹,

McCord²

2008

Journal of Magnetism and Magnetic Materials

233

134

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“…The direction of H eb can also be reversed if the magnetic field during bombardment is antiparallel to H eb,0 (and |H eb | can be increased or decreased depending on the ion dose [5]). IB may even initialize the macroscopic EB effect [6,7] as an additional method.…”

Section: Introductionmentioning

confidence: 99%

Fundamentals for magnetic patterning by ion bombardment of exchange bias layer systems

Ehresmann

Engel

Weis

et al. 2006

Physica Status Solidi (b)

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In the present paper we investigate whether the ion bombardment induced magnetic modifications in exchange biased bilayers are stable in time, whether the direction of the exchange bias can be set to any arbitrary (in-plane) direction by the ion bombardment and whether the exchange bias field can be changed in successive bombardment steps. These three fundamental characteristics are prerequisites for ion bombardment used for an efficient, practical, and stable magnetic patterning of exchange biased layer systems.

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“…[7,22,23,24]. We believe that it is an essential feature of all EB systems.Exchange-biased F/AF polycrystalline [25,26] bilayers Ir 17 M n 83 (15 nm)/Co 70 F e 30 (30 nm) were prepared by magnetron sputtering on Si/SiO2/Cu(30 nm) substrates, covered by a T a(5 nm) protection layer. The base pressure was below 1 × 10 −7 Torr at an Ar pressure of 3 × 10 −3 Torr.…”

mentioning

confidence: 99%

Quantitative description of the azimuthal dependence of the exchange bias effect

Radu¹,

Westphalen²,

Theis‐Bröhl³

et al. 2005

J. Phys.: Condens. Matter

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While the principal features of the exchange bias between a ferromagnet and an antiferromagnet are believed to be understood, a quantitative description is still lacking. We show that interface spin disorder is the main reason for the discrepancy of model calculations versus experimental results. Taking into account spin disorder at the interface between the ferromagnet and the antiferromagnet by modifying the well known Meiklejohn and Bean model, an almost perfect agreement can be reached. As an example this is demonstrated for the CoFe/IrMn exchange biased bilayer by analyzing the azimuthal dependence of magnetic hysteresis loops from MOKE measurements. Both, exchange bias and coercive fields for the complete 360• angular range are reproduced by our model. The exchange bias system refers to the shift of the ferromagnetic (F) hysteresis loop to positive or negative values when the F system is in contact with an antiferromagnetic (AF) system and cooled in an applied magnetic field through the Néel temperature of the AF system. The exchange bias (EB) phenomenon is associated with the interfacial exchange coupling between ferromagnetic and antiferromagnetic spin structures, resulting in a unidirectional magnetic anisotropy [1]. While the unidirectional anisotropy was successfully introduced by Meiklejohn and Bean (M&B), the origin of the enhanced coercive field is yet not well understood. The details of the EB effect depend crucially on the AF/F combination chosen and on the structure and thickness of the films [2,3]. However, some characteristic features apply to most systems: (1) H EB and H c increase as the system is cooled in an applied magnetic field below the blocking temperature T B ≤ T N of the AF layer, where T N is the Néel temperature of the AF layer; (2) the magnetization reversal can be different for the ascending and descending part of the hysteresis loop [4,5,6,7,8]; (3) thermal relaxation effects of H EB and H c indicate that a stable magnetic state is reached only at very low temperatures [9,10,11].Several theoretical models have been developed for describing possible mechanisms of the EB effect, including domain formation in the AF layer with domain walls perpendicular to the AF/F interface [12], creation of uncompensated excess AF spins at the interface [13], or the formation of domain walls in the AF layer parallel to the interface [14,15]. Another approach is the consideration of diluted antiferromagnets in an exchange field. In the work described in Ref. [16,17,18] the discussion about compensated versus uncompensated interfacial spins is replaced by a discussion of net magnetic moments within the antiferromagnetic layer. Depending on the complexity of the system, the models can explain some but not * florin.radu@bessy.de † Present address: BESSY GmbH, Albert-Einstein-Str. 15, D-12489 Berlin, Germany.all features of experimental hysteresis loops. Here we provide a new model which can describe all features, including the azimuthal dependence of H EB , H c , and the AF thickness dependence. In ...

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Influence of ion bombardment on transport properties and exchange bias in magnetic tunnel junctions

Cited by 25 publications

References 7 publications

Magnetic patterning by means of ion irradiation and implantation

Magnetic patterning by means of ion irradiation and implantation

Fundamentals for magnetic patterning by ion bombardment of exchange bias layer systems

Quantitative description of the azimuthal dependence of the exchange bias effect

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