Domain wall properties of FePt: From Bloch to linear walls

Hinzke, Denise; Kazantseva, Natalia E.; Nowak, Ulrich; Mryasov, O. N.; Asselin, Pierre; Chantrell, R.W.

doi:10.1103/physrevb.77.094407

Cited by 55 publications

(56 citation statements)

References 17 publications

(25 reference statements)

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“…For a DW at finite temperature, the free energy is ΔFðTÞ ¼ ΔU − TΔS, where ΔU is the internal energy and ΔS the entropy of the DW. It is a monotonically decreasing function of temperature [9][10][11]. This rather general argument explains a DW motion towards the hotter parts of the sample where the free energy is lower [11][12][13] and it can be expected to hold for other magnetic textures as well.…”

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confidence: 91%

Inertia-Free Thermally Driven Domain-Wall Motion in Antiferromagnets

et al. 2016

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Domain wall motion in antiferromagnets triggered by thermally induced magnonic spin currents is studied theoretically. It is shown by numerical calculations based on a classical spin model that the wall moves towards the hotter regions, as in ferromagnets. However, for larger driving forces the so called Walker breakdown which usually speeds down the wall is missing. This is due to the fact that the wall is not tilted during its motion. For the same reason antiferromagnetic walls have no inertia and, hence, no acceleration phase leading to higher effective mobility.The interest in antiferromagnetic and ferrimagnetic materials has increased recently for several reasons. One is the more complex spin structures which lead to additional spin wave modes with higher frequencies and, consequently, faster spin dynamics than in ferromagnets (FMs). Possible applications are in the field of ultrafast spin dynamics [1,2]. Also, ferrimagnets and antiferromagnets (AFMs) have attracted a lot of attention as low-damping, insulating magnets in the emerging field of spincaloritronics [3][4][5] which is on the combined transport of spin and heat. Finally, antiferromagnets are also discussed as future material for antiferromagnetic spintronics, since it has been shown that despite their lack of a macroscopic magnetization their magnetic state can be controlled via spin torque switching and can be read out via their magnetoresistive properties [6]. Spintronic phenomena call for exploitation in devices with magnetic storage functionalities, where a magnetic nanostructure has to be controlled efficiently and fast. The information can be stored in magnetic domains, in isolated magnetic nanoparticles, or even in domain walls (DWs) [7]. For the latter case synthetic AFMs have been shown to pave a new road towards higher DW mobility [8].For a ferromagnetic system, in Ref.[9] the existence of thermally driven domain-wall motion in temperature gradients was demonstrated by computer simulations based on different approaches, an atomistic spin model as well as a micromagnetic model based on the Landau-Lifshitz-Bloch (LLB) equation of motion. A thermodynamic explanation for this kind of DW motion rests on the minimization of the free energy of the DW (or the maximization of entropy). For a DW at finite temperature, the free energy is ΔFðTÞ ¼ ΔU − TΔS, where ΔU is the internal energy and ΔS the entropy of the DW. It is a monotonically decreasing function of temperature [9][10][11]. This rather general argument explains a DW motion towards the hotter parts of the sample where the free energy is lower [11][12][13] and it can be expected to hold for other magnetic textures as well. Furthermore, it has been shown by Schlickeiser et al.that the DW motion is caused by a so-called entropic torque. The exchange stiffness is weaker for higher temperature and therefore, an effective torque on the DW is created driving it towards the hotter region [11].A more microscopic explanation for DW motion in temperature gradients rests on the continuous stream of ...

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confidence: 91%

Inertia-Free Thermally Driven Domain-Wall Motion in Antiferromagnets

et al. 2016

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“…It is thus * Corresponding author: phxwan@ust.hk interesting to ask whether there is a general thermodynamic principle for thermal-gradient-driven DW motion. Previous theories [13,14,23] are based on magnon kinetics, multiscale micromagnetic framework, as well as spin model simulations. In this paper, the underlying thermodynamic principle of thermal-gradient-driven DW motion is revealed.…”

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Thermodynamic theory for thermal-gradient-driven domain-wall motion

Wang

2014

Phys. Rev. B

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Spin waves (or magnons) interact with magnetic domain walls (DWs) in a complicated way that a DW can propagate either along or against magnon flow. However, thermally activated magnons always drive a DW to the hotter region of a nanowire of magnetic insulators under a temperature gradient. We theoretically illustrate why it is surely so by showing that DW entropy is always larger than that of a domain as long as material parameters do not depend on spin textures. Equivalently, the total free energy of the wire can be lowered when the DW moves to the hotter region. The larger DW entropy is related to the increase of magnon density of states at low energy originated from the gapless magnon bound states. Manipulation of a magnetic domain wall (DW) in a nanostructure has attracted much attention due to its application prospects in logical operations [1] and data storage [2]. Moving DWs in a controlled manner is an important issue in those applications. Magnetic fields via energy dissipation [3][4][5] and electric current via angular momentum transfer [6][7][8] are well-known control parameters for DW motion. To overcome the Joule heating [7] in current driven magnetization reversal, heat itself has recently been proposed [9] as an efficient control parameter for spin manipulation. A temperature gradient can generate spin current [10][11][12] due to electron and/or magnon flow. This thermoelectric phenomenon of spin current generation is called spin Seebeck effect that has been experimentally observed through the inverse spin Hall effect [10]. The spin Seebeck effect has also been suggested [13,14] as a control parameter for DW manipulation. As spin-1 carriers, magnons can mediate a spin transfer torque (STT) [15] on a magnetic texture like a DW in a similar way as the electrons do. It was predicted [13,14] that a thermal-magnon-driven DW can propagate along a wire at a high speed, and this prediction was confirmed in a recent experiment [16].There is little doubt that magnonic STT can drive a DW to move. In terms of DW propagation direction, the pure magnonic STT predicts [15] a DW moving against magnon propagation direction. However, a DW may also propagate along magnon flow direction [17][18][19]. This is very similar to electric-current-driven DW motion: A DW propagates along or against electron flow direction, depending on detailed spin-orbit interactions and DW types [20][21][22]. It is not clear whether magnon-driven "wrong" DW propagation direction shares a similar physics origin as its electron counterpart. In principle, angular momentum does not dictate DW motion since its governing dynamics, Landau-Lifshitz-Gilbert (LLG) equation, does not conserve the total angular momentum when the spin-lattice and spin-orbital interactions are involved. Nevertheless, all studies [13,14,16] showed that a DW propagates to the hotter part of a wire under a temperature gradient. Although this result is consistent with the STT prediction, magnonic STT cannot be the sole physics behind. It is thus * Corresponding author: phxw...

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“…The wall width for MnAl was then calculated to be δ w ~10.9 nm, which was comparable to the values found in FePt (δ w =6 nm) [153] and CoCrPt (δ w =14 nm) [151]. By combining Eqs.…”

Section: Domain Wall Scattering Study In L1 0 Mnalsupporting

confidence: 66%

Magnetic Multilayer Structures for Spin Torque Nano Oscillator

Luo¹

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Domain wall properties of FePt: From Bloch to linear walls

Cited by 55 publications

References 17 publications

Inertia-Free Thermally Driven Domain-Wall Motion in Antiferromagnets

Inertia-Free Thermally Driven Domain-Wall Motion in Antiferromagnets

Thermodynamic theory for thermal-gradient-driven domain-wall motion

Magnetic Multilayer Structures for Spin Torque Nano Oscillator

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