Temperature dependence of magnetic anisotropy: An<i>ab initio</i>approach

Staunton, J. B.; Szunyogh, L.; Buruzs, Adam; Györffy, B. L.; Ostanin, S.; Udvardi, L.

doi:10.1103/physrevb.74.144411

Cited by 201 publications

(203 citation statements)

References 74 publications

(90 reference statements)

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“…Assuming a nucleation volume of cylindrical shape with the film thickness (37.5 nm) as the cylinder height, the estimated radius of the cylinder is ∼ 1.5 nm, on the order of the domain wall width. We should, however, take into consideration that E 0 b is the barrier at T = 107 K, where the magnetization is ∼ 0.7 of its saturation value and K u may also be suppressed [30,31]. Therefore, the volume could be larger although still on the same order.…”

Section: Resultsmentioning

confidence: 99%

Thermally assisted current-induced magnetization reversal in SrRuO3

et al. 2013

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We inject a sequence of 1 ms current pulses into uniformly magnetized patterns of the itinerant ferromagnet SrRuO3 until a magnetization reversal is detected. We detect the effective temperature during the pulse and find that the cumulative pulse time τ required to induce magnetization reversal depends exponentially on 1/T . In addition, we find that τ also depends exponentially on the current amplitude. These observations indicate current-induced magnetization reversal assisted by thermal fluctuations.

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Section: Resultsmentioning

confidence: 99%

Thermally assisted current-induced magnetization reversal in SrRuO3

et al. 2013

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“…These "local moment" degrees of freedom produce local magnetic fields centered at the lattice sites which in turn affect the electronic motions and are self-consistently maintained by them. The theory of Disordered Local Moments (DLM) in conjunction with the Korringa-Kohn-Rostoker Coherent Potential Approximation (KKR-CPA) was proposed twentyfive years ago by Györffy et al 10 and has recently been generalized by Staunton et al [17][18][19] to include relativistic effects. Here we give a short summary of the method as applied to the consideration of the paramagnetic state.…”

Section: B the Relativistic Disordered Local Moment Schemementioning

confidence: 99%

Atomistic spin model based on a spin-cluster expansion technique: Application to the IrMn3/Co interface

et al. 2011

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In order to derive tensorial exchange interactions and local magnetic anisotropies in itinerant magnetic systems, an approach combining the Spin-Cluster Expansion with the Relativistic Disordered Local Moment scheme is introduced. The theoretical background and computational aspects of the method are described in detail. The exchange interactions and site resolved anisotropy contributions for the IrMn3/Co(111) interface, a prototype for an exchange bias system, are calculated including a large number of magnetic sites from both the antiferromagnet and ferromagnet. Our calculations reveal that the coupling between the two subsystems is fairly limited to the vicinity of the interface. The magnetic anisotropy of the interface system is discussed, including effects of the Dzyaloshinskii-Moriya interactions that appear due to symmetry breaking at the interface.

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“…Our most remarkable observation is the surprisingly strong, second order MA of IrMn 3 resulting from the fact that the cubic symmetry is locally broken for each of the three Mn sub-lattices. We are also able to attribute contributions of the MAE related to on-site and two-site exchange anisotropy terms, a very important issue for finite temperature magnetism 6,7 . Such a separation is inevitably important for the purpose of subsequent simulations to study exchange-bias systems based on these compounds, for example in determining the scaling behavior of the MA energy.…”

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Giant magnetic anisotropy of the bulk antiferromagnets IrMn andIrMn3from first principles

et al. 2009

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Theoretical predictions of the magnetic anisotropy of antiferromagnetic materials are demanding due to a lack of experimental techniques which are capable of a direct measurement of this quantity. At the same time it is highly significant due to the use of antiferromagnetic components in magneto-resistive sensor devices where the stability of the antiferromagnet is of upmost relevance. We perform an ab-initio study of the ordered phases of IrMn and IrMn3, the most widely used industrial antiferromagnets. Calculating the form and the strength of the magnetic anisotropy allows the construction of an effective spin model, which is tested against experimental measurements regarding the magnetic ground state and the Néel temperature. Our most important result is the extremely strong second order anisotropy for IrMn3 appearing in its frustrated triangular magnetic ground state, a surprising fact since the ordered L12 phase has a cubic symmetry. We explain this large anisotropy by the fact that cubic symmetry is locally broken for each of the three Mn sub-lattices. While the magnetic anisotropy (MA) of ferromagnets is a well investigated quantity, both experimentally as well as theoretically, it is much less understood in case of antiferromagnets. This lack of knowledge is on the one hand due to a lack of experimental techniques which are capable of a direct measurement of this quantity. On the other hand, theoretical first principles calculations of magnetic anisotropy effects are quite challenging as they require the use of fully relativistic spin density functional theory.Interest in the MA of antiferromagnets comes from the fact that these compounds are important components of GMR sensors used, e.g., in hard disc read heads. Antiferromagnetic materials are employed in these devices to form antiferromagnet/ferromagnet bilayers exhibiting exchange bias 1 , a shift of the hysteresis loop of the ferromagnet, providing a pinned layer which fixes the magnetization of the reference layer of a GMR sensor. The stability of the antiferromagnet is most crucial for the stability of exchange bias and hence the functioning of the device 2,3 . Industrially the antiferromagnet IrMn is widely used because of the large exchange bias and thermal stability that can be obtained with this material.From experimental investigations of the exchange bias effect it is concluded that IrMn must have a rather large MA. Recent estimates of the MA of IrMn concerned the mean blocking temperature T B , the temperature at which the exchange bias shift changes sign upon thermal activation. From T B the intrinsic MA can be inferred if the particle size distribution is known; such a procedure has recently been reported and the room temperature MA energy of IrMn was estimated at 5.5×10 6 erg/cc 4 and even 2.8×10 7 erg/cc 5 depending on the seed layer and, consequently, the texture of the IrMn.In this letter, we address several features of the MA of IrMn alloys starting from first principles. In terms of simple symmetry considerations we predict the form...

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Temperature dependence of magnetic anisotropy: Anab initioapproach

Cited by 201 publications

References 74 publications

Thermally assisted current-induced magnetization reversal in SrRuO3

Thermally assisted current-induced magnetization reversal in SrRuO3

Atomistic spin model based on a spin-cluster expansion technique: Application to the IrMn3/Co interface

Giant magnetic anisotropy of the bulk antiferromagnets IrMn andIrMn3from first principles

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