Distribution of blocking temperature in bilayered Ni81Fe19/NiO films

Soeya, Susumu; Imagawa, T.; Mitsuoka, K.; Narishige, S.

doi:10.1063/1.358488

Cited by 130 publications

(91 citation statements)

References 12 publications

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“…Stiles and Me Michael [4] have recently proposed a model for polycrystalline samples in which AF grains are divided into two groups according to the e = iJo --K ratio where Jc is the average direct coupling between the AF and the F. Grains with low E contribute to the exchange bias whereas those with high E can induce coercive field. This theory is coherent with experimental studies made by S. Soeya et al in NiO/NiFe [5] bilayers who report that many "local domain paths" between TN(NiO) and room temperature are involved in the coupling. These paths can be "activated" reducing temperature.…”

Section: Introductionsupporting

confidence: 90%

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Exchange-Biased Nio-Co Nanofaceted Bilayers Grown on MgO (110)

et al. 2001

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We have sputter-grown self-organised faceted NiO-Co epitaxial bilayers on MgO( 110). Due to very close lattice parameters, NiO adopts the same NaC1 crystallographic structure as the substrate but it minimises its surface energy growing in a stripe-shaped morphology elongated along [001] MgO direction. The Co layers then deposited on NiO adopt a fcc structure. They consist of a set of connected nanowires whose height is about 50 A, length is near to I .tm and lateral periodicity = 100 A. Magnetic properties of the Co layers were investigated by magnetooptical Kerr effect from 10 K to room temperature. They are dominated by a strong shapeinduced uniaxial anisotropy and exchange coupling with the antiferromagnetic underlayer. Magnetisation loops recorded along the easy axis exhibit a perfect squareness and switch in a field range smaller than 10 Oe. Transverse measurements indicate that switching occurs by domain nucleation and/or domain wall propagation. On the contrary, close to the [110] hard axis, magnetic switching occurs by coherent rotation. The bi-stable Co magnetisation state along its easy axis has been used for ordering the NiO spins configuration from room temperature to 10 K. Sign and value of exchange bias induced by such a thermal treatment can be modulated thanks to a wide magnetocrystalline or local exchange path energies distributions.

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Section: Introductionsupporting

confidence: 90%

“…Such distribution has been previously observed by Soeya at al. [5] on polycristalline NiO/NiFe samples. They conclude that higher blocking temperature density is very close to the global blocking temperature near 215'C.…”

Section: Ti84mentioning

confidence: 99%

Exchange-Biased Nio-Co Nanofaceted Bilayers Grown on MgO (110)

et al. 2001

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“…I.C.3), whereas the Néel temperature is intrinsic to the antiferromagnet (Berkowitz and Takano, 1999;Nogués and Schuller, 1999). The blocking temperature can easily be determined experimentally, for example, by measuring the disappearance of the hysteresis loop shift as the external temperature rises, or by using specific field-cooling protocols (Soeya et al, 1994;Baltz, Rodmacq et al, 2010). In contrast, it is much more challenging to determine the Néel temperature for a thin film of isolated antiferromagnetic material.…”

Section: B Magnetic Phase Transition and Finite-size Scalingmentioning

confidence: 99%

Antiferromagnetic spintronics

et al. 2018

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Antiferromagnetic materials could represent the future of spintronic applications thanks to the numerous interesting features they combine: they are robust against perturbation due to magnetic fields, produce no stray fields, display ultrafast dynamics, and are capable of generating large magnetotransport effects. Intense research efforts over the past decade have been invested in unraveling spin transport properties in antiferromagnetic materials. Whether spin transport can be used to drive the antiferromagnetic order and how subsequent variations can be detected are some of the thrilling challenges currently being addressed. Antiferromagnetic spintronics started out with studies on spin transfer and has undergone a definite revival in the last few years with the publication of pioneering articles on the use of spin-orbit interactions in antiferromagnets. This paradigm shift offers possibilities for radically new concepts for spin manipulation in electronics. Central to these endeavors are the need for predictive models, relevant disruptive materials, and new experimental designs. This paper reviews the most prominent spintronic effects described based on theoretical and experimental analysis of antiferromagnetic materials. It also details some of the remaining bottlenecks and suggests possible avenues for future research. This review covers both spin-transfer-related effects, such as spin-transfer torque, spin penetration length, domain-wall motion, and "magnetization" dynamics, and spin-orbit related phenomena, such as (tunnel) anisotropic magnetoresistance, spin Hall, and inverse spin galvanic effects. Effects related to spin caloritronics, such as the spin Seebeck effect, are linked to the transport of magnons in antiferromagnets. The propagation of spin waves and spin superfluids in antiferromagnets is also covered.

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“…Sometimes the technique, developed by Soeya et al [26], is used to determine T B . With this method a sample is first field cooled to the temperature T m , then warmed up at zero field to a certain temperature, at which the magnetic field of the opposite sign is applied, and the sample is cooled back to T m at this field.…”

Section: Figmentioning

confidence: 99%

Characteristic temperatures of exchange biased systems

Dobrynin

Prozorov

2007

Journal of Applied Physics

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Characteristic temperatures in ferromagnetic -antiferromagnetic exchange biased systems are analyzed. In addition to usual blocking temperature of exchange bias TB, and the Néel temperature of an antiferromagnet TN , the inducing temperature T ind , i.e., the temperature, at which the direction of exchange anisotropy is established, has been recently proposed. We demonstrate that this temperature is in general case different from TB and TN . Physics and experimental approaches to measure the inducing temperature are discussed. Measurements of T ind , in addition to TB, and TN , provide important information about exchange interactions in ferromagnetic -antiferromagnetic heterostructures.PACS numbers: 75.30. Gw, 75.70.Cn, 75.30.Et, 75.50.Ee Exchange anisotropy appears in hybrid ferromagnetic (F) -antiferromagnetic (AF) systems due to exchange interactions at the F-AF interface [1]. The interfacial exchange creates an additional energy barrier, which F magnetic moments have to overcome during the magnetization reversal. The exchange anisotropy is unidirectional and shows up as a horizontal shift of the magnetic hysteresis loop after field cooling, and the exchange bias field is determined as the value to which the center of the hysteresis loop is shifted with respect to the zero field [2]. This assumes that the AF structure stays stable, which is valid unless the total AF magnetocrystalline anisotropy is too low, when AF spins rotate coherently with F spins, and the exchange bias vanishes [3,4,5]. The loop is normally shifted in the direction opposite to the cooling field, which indicates that the interfacial exchange coupling is ferromagnetic, i.e., it favors parallel orientation of the interfacial F and AF spins. The case of "positive" loop shifts, which may assume antiferromagnetic coupling at the F-AF interface (favoring antiparallel alignment of the interfacial F and AF spins), was described by Nogués et al. [6,7].It is a "common knowledge" that the exchange anisotropy is established when field cooling a F-AF system through the Néel temperature T N of the antiferromagnet [8,9]. The blocking temperature of exchange bias T B is the temperature, at which exchange bias disappears. It has been recently demonstrated that the direction of exchange anisotropy can be established at a temperature larger than T B , which is determined as exchange bias inducing temperature T ind [10].The procedure of measuring T ind is as follows. At first the sample is field cooled in a "negative" field −H F C from temperature T M (T M > T N ), to a certain temperature T switch , where the sign of the cooling field is changing. The further cooling to the temperature T m * Electronic address: dobrynin@ameslab. gov FIG. 1: Fig. 1. Exchange bias field H eb , measured at temperature Tm as a function of temperature T switch , at which the direction of the cooling field is changed from −HF C to +HF C . The temperature is scanning from TM down to Tm. In case of T ind < T switch < TM the exchange bias is negative (−Hm), since it's induced ...

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Distribution of blocking temperature in bilayered Ni81Fe19/NiO films

Cited by 130 publications

References 12 publications

Exchange-Biased Nio-Co Nanofaceted Bilayers Grown on MgO (110)

Exchange-Biased Nio-Co Nanofaceted Bilayers Grown on MgO (110)

Antiferromagnetic spintronics

Characteristic temperatures of exchange biased systems

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