Quantitative description of the azimuthal dependence of the exchange bias effect

Radu, F.; Westphalen, A.; Theis‐Bröhl, Katharina; Zabel, H.

doi:10.1088/0953-8984/18/3/l01

Cited by 86 publications

(61 citation statements)

References 36 publications

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“…A similar noncollinear configuration has already been used to model recent experimental observations in exchange-bias systems. [22][23][24][25] In our case, this is unambiguously deduced from the angular dependence of in-plane angle-resolved hysteresis loops, their asymmetry, and a fit to a modified Stoner-Wohlfarth ͑SW͒ model. Additional numerical simulations show that the new anisotropy naturally arises from the inevitable spin frustration at the atomically rough FM/AFM interface, which becomes important for vanishing FM anisotropy.…”

Section: Introductionsupporting

confidence: 56%

“…This mechanism of symmetry breaking by interfacial spin frustration confirms the need to use noncollinear anisotropy configurations, as was previously suggested. 23,25 In addition, our results give further insight into the microscopic mechanism due to the distinctively different behavior for systems with varying intrinsic anisotropy. Our findings hence provide a simple and general explanation, schematically depicted in Fig.…”

Section: Introductionmentioning

confidence: 71%

“…Asymmetries in the magnetization reversal have been observed for many FM/AFM systems with both in-plane [20][21][22][23][24][25][26][27][28][29][30][31][32][33][34] and perpendicular 35,36 anisotropy for the FM layer. In general, rotation processes are more relevant in one branch of the hysteresis loop, in which a larger density of domains during irreversible domain nucleation processes is also observed.…”

Section: Resultsmentioning

confidence: 98%

“…The asymmetric-shape behavior observed for Co/IrMn is well reproduced by considering collinear anisotropies. Surprisingly, although the field cooling was performed with the external field oriented parallel to the easy axis of the original FeNi uniaxial anisotropy, noncollinear anisotropies [22][23][24][25] with a significant misalignment ͑ = −20°͒ have to be considered to reproduce the hysteresis loops obtained for the FeNi/IrMn bilayers.…”

Section: Resultsmentioning

confidence: 99%

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Emergence of noncollinear anisotropies from interfacial magnetic frustration in exchange-bias systems

et al. 2009

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Exchange bias, referred to the interaction between a ferromagnet ͑FM͒ and an antiferromagnet ͑AFM͒, is a fundamental interfacial magnetic phenomenon, which is key to current and future applications. The effect was discovered half a century ago, and it is well established that the spin structures at the FM/AFM interface play an essential role. However, currently, ad hoc phenomenological anisotropies are often postulated without microscopic justification or sufficient experimental evidence to address magnetization-reversal behavior in exchange-bias systems. We advance toward a detailed microscopic understanding of the magnetic anisotropies in exchange-bias FM/AFM systems by showing that symmetry-breaking anisotropies leave a distinct fingerprint in the asymmetry of the magnetization reversal and we demonstrate how these emerging anisotropies are correlated with the intrinsic anisotropy. Angular and vectorial resolved Kerr hysteresis loops from FM/AFM bilayers with varying degree of ferromagnetic anisotropy reveal a noncollinear anisotropy, which becomes important for ferromagnets with vanishing intrinsic anisotropy. Numerical simulations show that this anisotropy naturally arises from the inevitable spin frustration at an atomically rough FM/AFM interface. As a consequence, we show in detail how the differences observed for different materials during magnetization reversal can be understood in general terms as originating from the interplay between interfacial frustration and intrinsic anisotropies. This understanding will certainly open additional avenues to tailor future advanced magnetic materials.

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Section: Introductionsupporting

confidence: 56%

Section: Introductionmentioning

confidence: 71%

Section: Resultsmentioning

confidence: 98%

Section: Resultsmentioning

confidence: 99%

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Emergence of noncollinear anisotropies from interfacial magnetic frustration in exchange-bias systems

et al. 2009

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“…When the reduced anisotropy is taken into account with a modification of the Meiklejohn and Bean model, 1,2 good quantitative agreement between model and experiment can be achieved. 23 Measurements of second harmonic generation from CoO/Cu/Fe multilayers have detected uncompensated spins at the CoO/Cu interface that are affected by the FM layer even across substantial Cu layer thickness. 24 Because of the presumed importance that AF domains have on exchange bias, several experiments have attempted to detect uncompensated magnetization of the domains directly.…”

Section: Introductionmentioning

confidence: 99%

Antiferromagnetic domain size and exchange bias

et al. 2008

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Using neutron diffraction, we measured the sizes of antiferromagnetic domains in three ferromagnet/ antiferromagnet bilayer samples as a function of the magnitude and sign of exchange bias, temperature, and antiferromagnet composition. Neutron-scattering techniques were applied to thin films with masses less than 10 g. We found the antiferromagnetic domain size to be consistently small regardless of the exchange bias. For a Co/untwinned single crystalline antiferromagnet ͑AF͒-fluoride bilayer, the antiferromagnetic domain size is comparable to the crystallographic domain size of the AF. For one sample the highest temperature at which the exchange bias was nonzero ͑i.e., the blocking temperature͒ was suppressed by ϳ3 K compared to the Néel temperature of the antiferromagnet.

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Interfacial Exchange Phenomena Driven by Ferromagnetic Domains

Díez

Cuñado

Lapa

et al. 2022

Adv Materials Inter

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to control most of the new properties observed in these artificial systems. [1] Despite the increasing progress in applications, a satisfactory microscopic knowledge of some fundamental physical aspects is still lacking. Paradigmatic is the case of the exchange interaction at the interface between an antiferromagnet (AFM) and a ferromagnet (FM), [2] which is used in most spintronic devices to pin (or stabilize) the magnetization of the adjacent thin FM film although there are still puzzles and experimental contradictions not well understood about its origin and effects. [2,3] The interfacial exchange coupling in AFM/FM systems was discovered and initially described by Meiklejohn and Bean in 1956. [4] Experimentally, when an AFM/ FM heterostructure is field cooled (FC) from above the Néel temperature (T N ) of the AFM layer, [2,4] and this undergoes the phase transition with the FM layer oriented in a certain direction, [5] an interfacial unidirectional anisotropy (K E ) is induced, which shifts the hysteresis loop away from zero field by the exchange bias field H E . The naivest picture fails in predicting a value of H E orders of magnitude larger than observed, or its vanishing at T N (while it often occurs at a smaller temperature, referred as blocking temperature T B ≤ T N .) The simple picture does not explain effects on the coercive field Interfacial proximity effects in antiferromagnetic/ferromagnetic (AFM/FM) bilayers control the exchange-bias (EB) phenomena exploited in most spintronic devices, although still is lack of full understanding. Discordant results, including different exchange-bias field (H E ), coercivity (H C ), or blocking temperature (T B ) found even in similar systems, are usually ascribed to uncontrolled parameters, namely dissimilar interfacial defects, structure, and thicknesses. Here, it is shown in the very same sample that the magnetic domain structure during the magnetization reversal of the FM layer controls those mentioned effects. Simultaneous transport and vectorial-resolved magnetic measurements performed in a V 2 O 3 /Co system during warming after different field cooling (FC) procedures exhibit a strong dependence on the FC angle and the domain structure of the FM layer. Remarkably, magnetization reversal analysis reveals 35 K of variation in T B and up to a factor of two in H E . These observations can be explained within the random-field model for the interfacial exchange coupling with a fixed AFM domain structure in contact with a variable (angle-dependent) FM domain structure. The results highlight the importance of the domain structure and magnetization reversal of the FM layer (not previously considered) in the EB phenomena, with potential to tailor interfacial effects in future spintronic devices.

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Quantitative description of the azimuthal dependence of the exchange bias effect

Cited by 86 publications

References 36 publications

Emergence of noncollinear anisotropies from interfacial magnetic frustration in exchange-bias systems

Emergence of noncollinear anisotropies from interfacial magnetic frustration in exchange-bias systems

Antiferromagnetic domain size and exchange bias

Interfacial Exchange Phenomena Driven by Ferromagnetic Domains

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