Thickness effect on ferro/antiferromagnetic coupling of Co/CrMnPt systems

Nishioka, K.; Shigematsu, S.; Imagawa, T.; Narishige, S.

doi:10.1063/1.367090

Cited by 40 publications

(17 citation statements)

References 7 publications

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“…As has been theoretically explained, 22 the largest grains have the highest H W values. Nishioka et al 23 observed that K AF increases with the increase of the particle size; as W ϳͱK AF , the same holds for H W . Thermal activation can also reduce H W when the grain size is decreased.…”

Section: 10mentioning

confidence: 67%

Frequency-dependent exchange bias in NiFe/NiO films

et al. 2003

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Ferromagnetic ͑FM͒ resonance and magnetization curve measurements were performed at room temperature for a polycrystalline Ni 81 Fe 19 coupled to NiO. It was observed that the shape of the angular variation of the resonance field is frequency dependent, with the curve at 9.65 GHz typical for a strongly exchange-coupled bilayer, while the 34.0 GHz curve is characteristic for relatively weak interactions. Numerical simulations of the resonance field and of the hysteresis loop shift, carried out through the domain wall formation model, as well as the resonance linewidth data indicated that there must be two fractions in the antiferromagnetic part of the interface, with stable and unstable grains. Only the stable grains contribute to the exchange bias. In our sample, whether an interfacial antiferromagnetic grain is stable or not is predominantly determined by the strength of the exhange coupling between this grain and the adjacent FM domain. The stable antiferromagnetic grains, whose contribution is sensed by the resonance experiment, are the smaller ones, which are more strongly coupled to the ferromagnet than the larger grains. The exchange-bias phenomenon, 1 which results from the interfacial coupling between ferromagnetic ͑FM͒ and antiferromagnetic ͑AF͒ materials, has been extensively studied in the last decade, motivated by fundamental and practical interests. One of the reasons for the continued interest is the fact that different experimental techniques may yield different exchange anisotropy values. [2][3][4][5][6][7][8][9] In some cases, this was assigned to the fact that the measurements are performed on different sets of samples. 4 Another source for the discrepancy could be the reliability of the model used in the experimental data interpretation. 8 It has also been shown 9 that the exchange-bias field values derived from magnetization and ferromagnetic resonance ͑FMR͒ measurements, must, in general, give different values in the framework of the domain-wall formation ͑DWF͒ model which assumes formation of a planar domain wall at the AF side of the interface with the reversal of the FM orientation. 8,10 Recent FMR studies on exchange-coupled NiFe films showed the importance of the magnetic state of the AF part of the interface. McMichael et al.11 used FMR to study the relaxation behavior of polycrystalline AF layer and found that the stability of the AF order is critical to the existence of the exchange bias. Relaxation related to thermally driven reversal of the AF grains in such systems has also been observed. 12,13The aim of the present work was to apply the phenomenological approach for the DWF model recently developed by our group 9 on a real exchange coupled system. The paper describes FMR and magnetization measurements of a bilayer of Permalloy ͑Py͒ ͑here, Ni 81 Fe 19 ) exchange-coupled to NiO. The striking frequency dependence of the FMR angular variation has been related to the relaxation behavior of the interfacial AF grains.The sample under investigation was deposited by rf magnetron sputterin...

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Section: 10mentioning

confidence: 67%

Frequency-dependent exchange bias in NiFe/NiO films

et al. 2003

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“…In the Mn-based system, the above-mentioned critical condition for the appearance of H EX was rarely observed in the AFM layer thickness dependence of H EX 33,34) and was not evident at all in its temperature dependence. Instead, the temperature dependences of H EX in other exchange-biased systems have often shown that H EX gradually decreases with increasing temperature and nally becomes zero at the blocking temperature [35][36][37][38][39] . This trend occurs because the thermal agitation of the AFM magnetization dominates the temperature dependence of the exchange bias.…”

Section: Perpendicular Exchange Bias Induced By Cr 2 O 3 (0001)mentioning

confidence: 99%

Perpendicular Exchange Bias and Magneto-Electric Control Using Cr<sub>2</sub>O<sub>3</sub>(0001) Thin Film

Shiratsuchi

Nakatani

2016

Mater. Trans.

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Antiferromagnets themselves do not generate either stray elds or spontaneous magnetization. However, if an antiferromagnet is coupled with a ferromagnet, unique and useful characteristics appear. Exchange bias is one such characteristic that is utilized in spintronic devices like spin-valve lms. To date, exchange bias has been used to induce static effects in devices; however, the exchange bias has not been switchable in these devices. Recently, switchable exchange bias has been developed using Cr 2 O 3 , which exhibits a magnetoelectric effect in an antiferromagnetic layer. The promising features of this effect are (1) the strength of the exchange bias is high and its direction is perpendicular to the lm, and (2) the switching is triggered by an electric eld. In this overview, we will summarize our recent results on the unique temperature dependence of high, perpendicular exchange bias and magnetoelectric switching of the induced perpendicular exchange bias.

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“…However, this conclusion runs counter to four experimental observations that suggest the AF film bulk is important to H E : ͑1͒ The AF film thickness must exceed a critical dimension ͑ϳ100 Å͒ in order to support exchange bias. 81,82 ͑2͒ The pinned magnetization in the AF bulk is an anchor for the unidirectional anisotropy giving rise to exchange bias. 32 …”

Section: B Characteristic Dimensions Of the Antiferromagnetic Domainmentioning

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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Thickness effect on ferro/antiferromagnetic coupling of Co/CrMnPt systems

Cited by 40 publications

References 7 publications

Frequency-dependent exchange bias in NiFe/NiO films

Frequency-dependent exchange bias in NiFe/NiO films

Perpendicular Exchange Bias and Magneto-Electric Control Using Cr<sub>2</sub>O<sub>3</sub>(0001) Thin Film

Antiferromagnetic domain size and exchange bias

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