Spin wave excitations in exchange biased IrMn/CoFe bilayers

Jenkins, Sarah; Chantrell, R.W.; Evans, Richard F. L.

doi:10.1063/5.0006232

Cited by 5 publications

(4 citation statements)

References 23 publications

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“…The increased understanding will provide possibilities for optimisation of exchange biased systems and the possible development of neuromorphic [33] and antiferromagnetic spintronic [34,35] devices. Our model also forms the basis of nanoscale antiferromagnetic spintonic device modelling including dynamics [36] that may provide further insights on electrically induced antiferromagnetic switching [37,38] and the operation of neuromorphic computing devices [39].…”

Section: Resultsmentioning

confidence: 99%

Exchange bias in multigranular noncollinear IrMn3/CoFe thin films

2021

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Antiferromagnetic spintronic devices have the potential to greatly outperform conventional ferromagnetic devices due to their ultrafast dynamics and high data density. A challenge in designing these devices is the control and detection of the orientation of the anti-ferromagnet. One of the most promising ways to achieve this is through the exchange bias effect. This is of particular importance in large scale multigranular devices. Previously, due to the large system sizes, only micromagnetic simulations of exchange have been possible, with an assumed a distribution of antiferromagnetic anisotropy directions and grain size. Here, we use an atomistic model where the distribution of antiferromagnetic anisotropy directions occurs naturally and where the exchange bias occurs due to the intrinsic disorder in the antiferromagnet. We perform large scale simulations of exchange bias, generating realistic values of exchange bias. We find a strong temperature dependence of the exchange bias in agreement with experimental observations, approaching zero at the blocking temperature of the antiferromagnet. We find that the experimentally observed increase in the coercivity at the blocking temperature occurs due to the superparamagnetic flipping of the antiferromagnet during the hysteresis loop cycle. We find a large discrepancy between the exchange bias predicted from a geometric model of the antiferromagnetic interface indicating the importance of grain edge effects in multigranular exchange biased systems. The grain size dependence of the shows the expected peak due to a competition between the superparamagnetic nature of small grains and reduction in the statistical imbalance in the number of interfacial spins for larger grain sizes. Our simulations confirm the existence of single antiferromagnetic domains within each grain. The model gives insights into the physical origin of exchange bias and provides a route to developing optimised nanoscale antiferromagnetic spintronic devices.

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Section: Resultsmentioning

confidence: 99%

Exchange bias in multigranular noncollinear IrMn3/CoFe thin films

2021

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“…If the magnonic component is not negligible, then a possible reason for why disentangling these contributions is more challenging for IrMn may be related to the shorter magnon characteristic lengths of 5 nm, as calculated in Ref. 53, compared to 9 nm for FeMn. In that case, our data would infer that both the magnonic and electronic lengths are comparable ($2 nm).…”

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confidence: 99%

Impact of gigahertz and terahertz transport regimes on spin propagation and conversion in the antiferromagnet IrMn

Gueckstock

Seeger

Seifert

et al. 2022

Applied Physics Letters

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Control over spin transport in antiferromagnetic systems is essential for future spintronic applications with operational speeds extending to ultrafast time scales. Here, we study the transition from the gigahertz (GHz) to terahertz (THz) regime of spin transport and spin-to-charge current conversion (S2C) in the prototypical antiferromagnet IrMn by employing spin pumping and THz spectroscopy techniques. We reveal a factor of 4 shorter characteristic propagation lengths of the spin current at THz frequencies (∼0.5 nm) as compared to GHz experiments (∼2 nm). This observation may be attributed to different transport regimes. The conclusion is supported by extraction of sub-picosecond temporal dynamics of the THz spin current. We identify no relevant impact of the magnetic order parameter on S2C signals and no scalable magnonic transport in THz experiments. A significant role of the S2C originating from interfaces between IrMn and magnetic or non-magnetic metals is observed, which is much more pronounced in the THz regime and opens the door for optimization of the spin control at ultrafast time scales.

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“…Among the AF systems with kagome spin structures there are several compounds with the jarosite crystal structure [17], pyrochlore oxides with all-in-all-out magnetic order [18][19][20], and noncollinear chiral AFs of the Mn 3 X (X = Sn, Ge, Ga, Ir, Pt, Rh) family [21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38]. In all these systems, the macroscopic degeneracy of the 120 • structure is lifted by some type of magnetic anisotropy, such as single-ion, magnetic dipole-dipole, or Dzyaloshinskii-Moriya interaction.…”

Section: Introductionmentioning

confidence: 99%

“…These techniques have a big advantage over inelastic neutron scattering because they can be implemented in small size equipment in research laboratories. One difficulty for a direct interpretation of the measured magnon frequencies is that due to the complex spin structures, the spin wave calculations for these materials are carried out by numerical procedures [28,31,32]. In this paper we present a spin-wave calculation for kagome AFs with exchange and single-ion anisotropy interactions that yield exact analytical expressions for the frequencies of magnons at high-symmetry point of the Brillouin zone, that can be readily use to obtain the interaction parameters from experimental data.…”

Section: Introductionmentioning

confidence: 99%

Analytical solutions for the magnon frequencies at high-symmetry points of the Brillouin zone in anisotropic kagome antiferromagnets

Rodrı́guez-Suárez¹,

Rezende²

2021

J. Phys.: Condens. Matter

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The knowledge of the magnon dispersion relations in antiferromagnetic materials with nontrivial spin textures has considerable interest to the understanding of magnonic and spintronic phenomena involving these materials. One particularly interesting nontrivial spin texture existing in several antiferromagnets has spins at an angle of 120 • with the in-plane neighbors and arranged in kagome lattices. Here we present a spin-wave calculation for antiferromagnets with kagome spin lattices considering exchange and single-ion anisotropy interactions between the spins. The theory yields exact analytical expressions for the frequencies of magnons at high-symmetry points of the Brillouin zone, that can be readily use to obtain the interaction parameters from experimental data with one-and two-magnon inelastic light scattering. The analytical expressions are used to obtain the field parameters for the kagome lattice antiferromagnet L1 2 -IrMn 3 from four experimentally measured frequencies. Both exchange field parameters are in reasonable agreement with the values obtained with ab initio calculations, while the anisotropy field is in very good agreement with the one calculated with atomistic spin models and Monte Carlo simulations.

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Spin wave excitations in exchange biased IrMn/CoFe bilayers

Abstract: Paper published as part of the special topic on Antiferromagnetic Spintronics Note: This paper is part of the special topic on Antiferromagnetic Spintronics.

Cited by 5 publications

References 23 publications

Exchange bias in multigranular noncollinear IrMn3/CoFe thin films

Exchange bias in multigranular noncollinear IrMn3/CoFe thin films

Impact of gigahertz and terahertz transport regimes on spin propagation and conversion in the antiferromagnet IrMn

Analytical solutions for the magnon frequencies at high-symmetry points of the Brillouin zone in anisotropic kagome antiferromagnets

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