Annealing influence on the Gilbert damping parameter and the exchange constant of CoFeB thin films

Conca, A.; Papaioannou, Evangelos Th.; Klingler, Stefan; Greser, J.; Sebastian, Tina; Leven, B.; Lösch, J.; Hillebrands, B.

doi:10.1063/1.4875927

Cited by 76 publications

(48 citation statements)

References 15 publications

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“…Therefore, permalloy was intensively used for the investigation of spin-wave physics in microstructures (see reviews [135,136]) and for invest igations of magnonic crystals in particular [3,5,7,134,137]. Nowadays, considerable attention from the community is also focused on CoFeB [138][139][140][141][142] and half-metallic Heusler compounds [143][144][145][146][147][148][149][150]. These materials possess smaller Gilbert damping parameter values and larger values of saturation magnetization, and, therefore, are more suitable for the purposes of magnonics.…”

Section: Magnetic Materials For Magnonic Applicationsmentioning

confidence: 99%

Magnonic crystals for data processing

Chumak

Serga

Hillebrands

2017

J. Phys. D: Appl. Phys.

437

320

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IntroductionThis article focuses on a selection of results in the field of magnonic crystals obtained within the last decade in our group. Special attention is devoted to the application of magnonic crystals in data processing and information technologies. Because of the large number of achievements in the field, it is unavoidable that many important results are excluded from this article. Therefore, we would like to direct the reader's attention to excellent reviews devoted to different aspects of magnonic crystals: spin-wave dynamics in periodic structures for microwave applications [1, 2], Brillouin light scattering (BLS) studies of planar metallic magnonic crystals [3], micromagnetic computer simulations of width-modulated waveguides [4], photo-magnonic aspects of antidot lattices studies [5], theoretical studies of one-dimensional monomode waveguides [6], and reconfigurable magnonic crystals [7]. The results presented in the current review were already partially presented in our own reviews of yttrium iron garnet (YIG) magnonics [8] and magnon spintronics [9] as well as in book chapters on dynamic magnonic crystals [10] and magnon spintronics [11].The article is organized in the following way: In the introduction we describe the field of magnon spintronics and discuss the role of magnonic crystals in it. The next section 2 is devoted to the properties of spin waves in thin planar films and waveguides, to the magnetic materials commonly used in the field, and to the methods of spin-wave excitation and detection. Sections 3 and 4 are devoted to the study of physical phenomena taking place in static and dynamic magnonic crystals, respectively. The application of magnonic crystals for magnonbased processing of analog and digital data is discussed in section 5. Specifically, static magnonic crystals can be used as passive elements, like microwave filters, resonators or delay lines for microwave generation. Reconfigurable and dynamic magnonic crystals are promising as active devices performing, for example, tunable filtering, frequency conversion or time reversal. In the final section we briefly summarize the results. Magnon spintronics: from electron-to magnon-based computingA disturbance in the local magnetic order can propagate in a magnetic material in the form of a wave. This wave was first predicted by Bloch in 1929 and was named spin wave since AbstractMagnons (the quanta of spin waves) propagating in magnetic materials with wavelengths at the nanometer-scale and carrying information in the form of an angular momentum can be used as data carriers in next-generation, nano-sized low-loss information processing systems. In this respect, artificial magnetic materials with properties periodically varied in space, known as magnonic crystals, are especially promising for controlling and manipulating magnon currents. In this article, different approaches for the realization of static, reconfigurable, and dynamic magnonic crystals are presented along with a variety of novel wave phenomena discovered in these cryst...

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Section: Magnetic Materials For Magnonic Applicationsmentioning

confidence: 99%

Magnonic crystals for data processing

Chumak

Serga

Hillebrands

2017

J. Phys. D: Appl. Phys.

437

320

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“…It has been known that the crystalline CoFeB film in MTJs has enhanced spin tunneling efficiency and hence can exhibit a higher TMR ratio than the corresponding amorphous one [12]. Therefore, an annealing process is required to induce crystallization of the as-deposited amorphous CoFeB films to increase TMR ratio [13][14][15]. Lots of works are focused on annealing effects on structural, magnetic and spin dynamic properties of CoFeB films [16][17][18][19][20].…”

Section: Introductionmentioning

confidence: 99%

Magnetic, thermal, electrical properties and crystallization kinetics of Co60Fe20B20 alloy films

Wang

Huang

et al. 2016

Sci. China Mater.

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Magnetic, thermal and electrical properties of sputtered Co60Fe20B20 alloy films are investigated. An excellent linear relationship between the saturation magnetization per unit area and thickness is obtained in the as-deposited film with thickness ranging from 10 to 100 nm. For the as-deposited films a high effective saturation magnetization of 793.7 ± 42.9 emu cm −3 is derived from the fitting. An in-plane uniaxial magnetic anisotropy of~10 4 erg cm −3 in magnitude is revealed by angular dependent magnetic measurements. A fourfold cubic magnetic anisotropy is found to develop with annealing, in line with the improvement of the crystalline structure in the film confirmed by X-ray diffraction measurements. Thermomagnetic measurements reveal a considerable variation of the saturation magnetization with temperature arising from the competition of the crystallization and the temperature dependent ferromagnetic behavior of the alloy film. Pronounced changes in electrical resistivity with temperature were observed in the alloy film, in accompany with the structural change. The activation barrier for crystallization was determined to be 1.43 eV from the electrical measurements with variable heating rates, showing a good thermal stability of the alloy film.

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“…For the thickness used in this work (40 nm) and physically reasonable K ⊥ S values, the influence of the interface is negligible and therefore M eff ≈ M S . For details about the estimation of M eff the reader is referred to [12]. Figure 2 shows the obtained values for M S for all samples.…”

Section: Orientationmentioning

confidence: 99%

“…For this, the samples were placed face down and the S 12 transmission parameter was recorded. A more detailed description of the FMR measurement and analysis procedure is shown in previous work [11,12]. Brillouin light spectroscopy (BLS) was additionally used for the measurement of the exchange constant.…”

mentioning

confidence: 99%

CoFeAlB alloy with low damping and low magnetization as a candidate for spin transfer torque switching

Conca

Nakano

Meyer

et al. 2017

Journal of Applied Physics

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We investigate the effect of Al doping on the magnetic properties of the alloy CoFeB. Comparative measurements of the saturation magnetization, the Gilbert damping parameter α and the exchange constant as a function of the annealing temperature for CoFeB and CoFeAlB thin films are presented. Our results reveal a strong reduction of the magnetization for CoFeAlB in comparison to CoFeB. If the prepared CoFeAlB films are amorphous, the damping parameter α is unaffected by the Al doping in comparison to the CoFeB alloy. In contrast, in the case of a crystalline CoFeAlB film, α is found to be reduced. Furthermore, the x-ray characterization and the evolution of the exchange constant with the annealing temperature indicate a similar crystallization process in both alloys. The data proves the suitability of CoFeAlB for spin torque switching properties where a reduction of the switching current in comparison with CoFeB is expected.The alloy CoFeB is widely used in magnetic tunneling junctions in combination with MgO barriers due to the large magnetoresistance effect originating in the spin filtering effect [1][2][3][4]. For the application in magnetic random access memories, the switching of the magnetization of the free layer via spin transfer torque (STT) with spin polarised currents is a key technology. However, the required currents for the switching process are still large and hinder the applicability of this technique. The critical switching current density for an in-plane magnetized system is given by [5]where e is the electron charge, α is the Gilbert damping parameter, M S is the saturation magnetization, t f is the thickness of the free layer, H ext is the external field, H K is the effective anisotropy field and η is the spin transfer efficiency. From the expression it is clear that, concerning material parameters, J c0 is ruled by the product αM 2 S . For out-of-plane oriented layers, the term 2πM S vanishes and then J C0 is proportional to αM S [6]. Even in the case of using pure spin currents created by the Spin Hall effect, the required currents are proportional to factors of the form α n M S with n = 1, 1/2 [7]. A proper strategy to reduce the critical switching currents is then defined by reducing the saturation magnetization. This can be achieved by the development of new materials or the modification of known materials with promising properties. Since the compatibility with a MgO tunneling barrier and the spin filtering effect must be guaranteed together with industrial applicability, the second option is clearly an advantage by reducing M S in the CoFeB alloy. In this case, a critical point is that this reduction must not be associated with an increase of the damping parameter α.

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Annealing influence on the Gilbert damping parameter and the exchange constant of CoFeB thin films

Cited by 76 publications

References 15 publications

Magnonic crystals for data processing

Magnonic crystals for data processing

Magnetic, thermal, electrical properties and crystallization kinetics of Co60Fe20B20 alloy films

CoFeAlB alloy with low damping and low magnetization as a candidate for spin transfer torque switching

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