Magnetic properties and domain structure of ultrathin yttrium iron garnet/Pt bilayers

Mendil, Johannes; Trassin, Morgan; Bu, Quingquing; Schaab, Jakob; Baumgärtner, Michael; Murer, Christoph; Phuong, Dao; Vijayakumar, Jaianth; Bracher, David; Bouillet, Corinne; Vaz, C. A. F.; Fiebig, Manfred; Gambardella, Pietro

doi:10.1103/physrevmaterials.3.034403

Cited by 38 publications

(27 citation statements)

References 65 publications

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“…A similar behavior for 4πM s was reported for thin PLD or magnetron-sputtered YIG films, and different explanations were given [76,56,91]. One reason for a reduced saturation magnetization could be an intermixing of substrate and film elements at the GGG/YIG interface, whereby a gradual change of the film composition is assumed [75,77]. In particular, gallium ion diffusion into the first YIG atomic layers will lead to magnetically diluted ferrimagnetic layers at the interface, due to the fact, that magnetic Fe ions are replaced by diamagnetic Ga ions in the various magnetic sublattices.…”

Section: Thickness-dependent Analysis Of the Effective Magnetization mentioning

confidence: 54%

“…Using the 10%-to-90% edge response criterion, it shows a transition width of (1.9 ± 0.4) nm at the interface. This is lower than the observed 4-6 nm non-magnetic dead layer reported for YIG films deposited by RF magnetron sputtering [76], and the about 4 nm or the 5-7 nm deep Ga diffusion observed for PLD [77] or laser molecular beam epitaxy (MBE) [75], respectively. However, at some positions of the sample's cross-section we found a reduced YIG film thickness on a wavy GGG surface (not shown), which we attribute to a possible etch-back of the substrate at the beginning of film growth or an already existing wavy substrate surface.…”

Section: Crystalline Perfection Studied By High-resolution Transmissimentioning

confidence: 66%

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Low damping and microstructural perfection of sub-40nm-thin yttrium iron garnet films grown by liquid phase epitaxy

Dubs

Surzhenko

Thomas

et al. 2020

Phys. Rev. Materials

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The field of magnon spintronics is experiencing an increasing interest in the development of solutions for spin-wave-based data transport and processing technologies that are complementary or alternative to modern CMOS architectures. Nanometer-thin yttrium iron garnet (YIG) films have been the gold standard for insulator-based spintronics to date, but a potential process technology that can deliver perfect, homogeneous large-diameter films is still lacking. We report that liquid phase epitaxy (LPE) enables the deposition of nanometer-thin YIG films with low ferromagnetic resonance losses and consistently high magnetic quality down to a thickness of 20 nm. The obtained epitaxial films are characterized by an ideal stoichiometry and perfect film lattices, which show neither significant compositional strain nor geometric mosaicity, but sharp interfaces. Their magneto-static and dynamic behavior is similar to that of single crystalline bulk YIG. We found, that the Gilbert damping coefficient α is independent of the film thickness and close to 1 × 10 -4 , and that together with an inhomogeneous peak-to-peak linewidth broadening of ∆H 0|| = 0.4 G, these values are among the lowest ever reported for YIG films with a thickness smaller than 40 nm. These results suggest, that nanometer-thin LPE films can be used to fabricate nano-and micro-scaled circuits with the required quality for magnonic devices. The LPE technique is easily scalable to YIG sample diameters of several inches.

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Section: Thickness-dependent Analysis Of the Effective Magnetization mentioning

confidence: 54%

Section: Crystalline Perfection Studied By High-resolution Transmissimentioning

confidence: 66%

Low damping and microstructural perfection of sub-40nm-thin yttrium iron garnet films grown by liquid phase epitaxy

Dubs

Surzhenko

Thomas

et al. 2020

Phys. Rev. Materials

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“…Several models have dealt with micromagnetic calculations of the magnetization distribution within zigzag walls, and some models have also included the dynamic hysteresis from such walls [ 30 , 31 , 32 ]. Charged zigzag domain walls have been observed in different systems, such as CoGd and CoGdNi [ 33 ], including, more recently, pulsed laser-deposited Co thin films [ 34 , 35 ] (and references therein), epitaxial Fe films grown on GaAs [ 36 ], permalloy/niobium bilayers [ 37 ], SmCo amorphous films [ 38 ], FePt thin films [ 39 ], CoFeB antiferromagnetically coupled layers [ 40 ], ultrathin yttrium iron garnet/Pt bilayers [ 41 ], single crystals of ferromagnetic shape memory Co 50 Ni 20 FeGa 29 alloy [ 42 ], and highly anisotropic CoFeB thin films [ 43 ]. However, to date, no experimental research has shown the transition from Néel- to Bloch-type cores with the formation of crosstie cores in Fe-charged domain walls.…”

Section: Introductionmentioning

confidence: 99%

Surface Roughness Influence on Néel-, Crosstie, and Bloch-Type Charged Zigzag Magnetic Domain Walls in Nanostructured Fe Films

2020

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Charged magnetic domain walls have been visualized in soft magnetic nanostructured Fe thin films under both static and dynamic conditions. A transition in the core of these zigzagged magnetic walls from Néel-type to Bloch-type through the formation of crosstie walls has been observed. This transition in charged zigzagged walls was not previously shown experimentally in Fe thin films. For film thicknesses t < 30 nm, Néel-type cores are present, while at t ≈ 33 nm, walls with crosstie cores are observed. At t > 60 nm, Bloch-type cores are observed. Along with the visualization of these critical parameters, the dependence on the film thickness of the characteristic angle and length of the segments of the zigzagged walls has been observed and analyzed. After measuring the bistable magneto-optical behavior, the values of the wall nucleation magnetic field and the surface roughness of the films, an energetic fit to these nucleation values is presented.

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“…The switching efficiency decreases in films thicker than 7 nm, which we attribute to a change of the domain morphology and increased pinning of the magnetic domain walls. 34 Strain engineering of YIG thin films may be used to further tailor the magnetic anisotropy 40 and hence the switching behavior of YIG in response to current-induced fields of either Oersted or spin-orbit origin. Our results should also be taken as a cautionary warning about the possible undesired switching of YIG at current densities commonly used to excite and sense the magnetization of Pt/YIG bilayers.…”

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confidence: 99%

Current-induced switching of YIG/Pt bilayers with in-plane magnetization due to Oersted fields

Mendil

Trassin

et al. 2019

Applied Physics Letters

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We report on the switching of the in-plane magnetization of thin yttrium iron garnet (YIG)/Pt bilayers induced by an electrical current. The switching is either field-induced and assisted by a dc current, or currentinduced and assisted by a static magnetic field. The reversal of the magnetization occurs at a current density as low as 10 5 A/cm 2 and magnetic fields of ∼ 40 µT, two orders of magnitude smaller than in ferromagnetic metals, consistently with the weak uniaxial anisotropy of the YIG layers. We use the transverse component of the spin Hall magnetoresistance to sense the magnetic orientation of YIG while sweeping the current. Our measurements and simulations reveal that the current-induced effective field responsible for switching is due to the Oersted field generated by the current flowing in the Pt layer rather than by spin-orbit torques, and that the switching efficiency is influenced by pinning of the magnetic domains.The possibility of manipulating the magnetization of planar structures using electrical currents opens exciting perspectives in spintronics. Electrical currents can affect the magnetization of thin films through the Oersted magnetic field, 1-5 spin transfer torques, 6 and spinorbit torques. 7 Previous work has focused on magnetization switching and domain wall dynamics induced by spin-orbit torques in metallic ferromagnets adjacent to a heavy metal layer. [8][9][10][11][12][13][14][15] Recently, investigations extended towards insulating ferrimagnetic garnets, which, owing to the low magnetic damping, are particularly appealing for generating and transmitting spin waves 16-19 as well as for magnetization switching. [20][21][22] The most prominent exponent of this material class is yttrium iron garnet (YIG). Extensive work on the interplay of current-induced effects and magnetization dynamics in YIG/Pt bilayers demonstrated efficient spin-wave excitations, 23-27 spinwave amplification, 28,29 and the control of magnetization damping. 30 So far, however, no attempt at currentinduced magnetization switching of YIG has been reported. Two plausible reasons for the scarcity of results in this area are the extreme sensitivity of YIG to magnetic fields, which makes it difficult to control the intermediate magnetization states, as well as to the need to utilize YIG films with uniaxial in-plane anisotropy, which is required to achieve binary switching. Indeed, the electrical switching of garnet insulators has been reported only for thin films with relatively large perpendicular anisotropy, such as thulium iron garnet layers in combination with either Pt or W. [20][21][22] In this paper, we investigate the reciprocal effects of current and magnetic field on the switching of YIG/Pt bilayers with in-plane magnetic anisotropy. We demonstrate field-induced switching assisted by a dc current as well as current-induced switching assisted by a static magnetic field at extremely low current density (∼ 10 5 A/cm 2 ) and bias fields (40 − 60 µT). We further show that the magnetization reversal can be sensed...

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Magnetic properties and domain structure of ultrathin yttrium iron garnet/Pt bilayers

Cited by 38 publications

References 65 publications

Low damping and microstructural perfection of sub-40nm-thin yttrium iron garnet films grown by liquid phase epitaxy

Low damping and microstructural perfection of sub-40nm-thin yttrium iron garnet films grown by liquid phase epitaxy

Surface Roughness Influence on Néel-, Crosstie, and Bloch-Type Charged Zigzag Magnetic Domain Walls in Nanostructured Fe Films

Current-induced switching of YIG/Pt bilayers with in-plane magnetization due to Oersted fields

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