Magnetic anisotropy energy and interlayer exchange coupling in ultrathin ferromagnets: Experiment versus theory

Baberschke, K.

doi:10.1080/14786430802279778

Cited by 9 publications

(6 citation statements)

References 33 publications

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“…It cannot be related to misoriented Ni crystalline axes, since the mosaicity of the epitaxied NWs is ≤4 • , as established by our structural analysis. Experiments and calculations on ultrathin Ni layers [22,23] show that a tetragonalization of the crystal goes along with a tetragonal magnetic symmetry. For the present case, only slight differences might be distinguished between the IP [100] and [110] directions when approaching saturation (Fig.4).…”

Section: Origin Of the Magnetic Anisotropy 321 Results At Low Tempmentioning

confidence: 98%

Magnetoelastic effects and random magnetic anisotropy in highly strained ultrathin Ni nanowires epitaxied in a SrTiO3 matrix

Weng

Hennes

Hrabovský³

et al. 2020

Journal of Magnetism and Magnetic Materials

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We analyze the magnetic anisotropy of Ni nanowires with diameters smaller than 5 nm. The nanowires are vertically epitaxied in a SrTiO 3 (001) matrix which generates huge tensile strains up to 3.6% along the nanowire axis. This leads to an unusual anisotropy, characterized by an easy magnetization plane perpendicular to the nanowire axis. Hysteresis cycles M(H) unveil an overall in-plane isotropy, while an opening of the M(H) cycles and thermal activation measurements indicate the presence of local energy barriers inside the nanowires. Surprisingly, the coercive field H c (T) decays exponentially with increasing temperature, for both the easy plane and the hard axis. Based on these findings, we provide an analysis of magnetoelastic effects in the nanowires. By considering global averaging over the anisotropy distribution and local averaging according to the Random Magnetic Anisotropy model, we find that the global anisotropy, with its hard axis and isotropic easy plane, is related to the mean strain, while coercivity arises from local strain variations. We evidence that a thermally activated anisotropy softening occurs in the nanowires, in addition to Sharrock's law of thermal reduction of coercivity. Possible mechanisms responsible for this thermal softening of anisotropy are proposed and discussed. Our study eventually allows to identify two major competing effects at play in the present system: an increasing magnetic anisotropy with increasing strain and a reduction of the anisotropy with increasing local strain fluctuations.

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Section: Origin Of the Magnetic Anisotropy 321 Results At Low Tempmentioning

confidence: 98%

Magnetoelastic effects and random magnetic anisotropy in highly strained ultrathin Ni nanowires epitaxied in a SrTiO3 matrix

Weng

Hennes

Hrabovský³

et al. 2020

Journal of Magnetism and Magnetic Materials

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“…However, modifying barrier properties in a trilayer thin film configuration with film thickness in few monolayer ranges exhibited intriguing effect of inter-electrode exchange coupling. In a related study, reducing the thickness of nonmagnetic metallic spacer between the two FM electrodes to few monolayers produced dramatic changes in the Curie temperature of the constituents FM electrodes [18,35]. Importantly, this (Fig.…”

Section: B-c) Covalent Bonding Of Omcs Tomentioning

confidence: 84%

Molecule Induced Strong Coupling between Ferromagnetic Electrodes of a Molecular Spintronics Device

Tyagi

2012

MSF

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Multilayer edge molecular spintronics device (MEMSD) approach can produce novel logic and memory units for the computers. MEMSD are produced by bridging the molecular channels across the insulator, in the exposed edge region(s) of a magnetic tunnel junction (MTJ). The bridged molecular channels start serving as the dominant exchange coupling medium between the two ferromagnetic electrodes of a MTJ. Present study focus on the effect of molecule enhanced exchange coupling on the magnetic properties of the MTJ. This paper shows that organometallic molecular clusters (OMCs) strongly increased the magnetic coupling between the two ferromagnetic electrodes. SQUID magnetometer showed that OMCs transformed the typical hysteresis magnetization curve of a Co/NiFe/AlOx/NiFe MTJ into linear one. Ferromagnetic resonance studies showed that OMC bridges affected the two fundamental resonance peaks of the Co/NiFe/AlOx/NiFe MTJ. According to magnetic force microscopy, OMCs caused the disappearance of magnetic contrast from the Co/NiFe/AlOx/NiFe tunnel junction area. These three independent and complimentary experiments, suggested the development of extremely strong interlayer exchange coupling. This work delineated a practical route to control the exchange coupling between ferromagnetic electrodes. Ability to tailor magnetic coupling can lead to the development of molecule based quantum computation device architecture. Introduction: Molecular spintronics devices (MSDs) are promising to produce new computer logic and advanced spintronics devices. According to theoretical and experimental studies, MSDs are shown to possess several new remarkable attributes which are not observed with conventional magneto resistance devices. MSDs' development will critically depend on the Hard OMC Soft AlOx J J J J J J          (6) Here, J Soft-OMC (J Hard-OMC ) is the exchange coupling between OMC and soft (hard) FM electrode, and J AlOx is the inter-electrode exchange coupling via ~ 2 nm AlOx insulator. In the present case J AlOx << J Soft-OMC or J Hard-OMC . Assuming, J Soft-OMC ≈ J Hard-OMC and using the estimate of OMCs induced J from table 1 we found that J Soft-OMC or J Hard-OMC is of the order of ~22 erg/cm 2 . TheOMCs induced exchange coupling is 3-4 orders higher than the exchange coupling produced by the nanoclusters.

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“…21c) and with the Ta top layer (Fig. 21d) corresponded to the weak antiferromagnetic and the ferromagnetic couplings, respectively [38]. OMCs on these two types of MTJ dots produced opposite effect, presumably because of the inherent difference in the nature of coupling, across the AlOx insulator.…”

Section: J (Exchange Coupling) = Saturation Field X Saturation Magnet...mentioning

confidence: 89%

“…To investigate the effect of OMCs induced coupling on P it is prudent to check if strong exchange coupling is capable of affecting the basic magnetic properties like Curie temperature, which depends on the spin DOS of FM electrodes. Experimentally, strong exchange coupling was found to change the Curie temperature of the FM electrodes by ~40 K when the thickness of the non-magnetic spacer between them was reduced to few monolayer [38]. Like the case of Kondo level splitting on a MSD [14], effect of exchange coupling on Curie temperature [23] was attributed to the spin fluctuations.…”

Section: J (Exchange Coupling) = Saturation Field X Saturation Magnet...mentioning

confidence: 90%

Room Temperature Current Suppression on Magnetic Tunnel Junction Based Molecular Spintronics Devices

Tyagi

2013

MRS Proc.

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Molecular conduction channels between two ferromagnetic electrodes can produce strong exchange coupling and dramatic effect on the spin transport, thus enabling the realization of novel logic and memory devices. However, fabrication of molecular spintronics devices is extremely challenging and inhibits the insightful experimental studies. Recently, we produced Multilayer Edge Molecular Spintronics Devices (MEMSDs) by bridging the organometallic molecular clusters (OMCs) across a ~2 nm thick insulator of a magnetic tunnel junction (MTJ),

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Magnetic anisotropy energy and interlayer exchange coupling in ultrathin ferromagnets: Experiment versus theory

Cited by 9 publications

References 33 publications

Magnetoelastic effects and random magnetic anisotropy in highly strained ultrathin Ni nanowires epitaxied in a SrTiO3 matrix

Magnetoelastic effects and random magnetic anisotropy in highly strained ultrathin Ni nanowires epitaxied in a SrTiO3 matrix

Molecule Induced Strong Coupling between Ferromagnetic Electrodes of a Molecular Spintronics Device

Room Temperature Current Suppression on Magnetic Tunnel Junction Based Molecular Spintronics Devices

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