Magnetoresistance of non-180° domain wall in the presence of electron-photon interaction

International Nano Letters, Aug 2013

In the present paper, influence of photon on resistance of non-180° domain wall in metallic magnetic nanowires has been studied using the semiclassical approach. The analysis has been based on the Boltzmann transport equation, within the relaxation time approximation. The one-dimensional Néel-type domain wall between two ferromagnetic domains with relative magnetization angle less than 180° is considered. By increasing this angle, the contribution of the domain wall in the resistivity of the nanowire becomes considerable. It is also found that the fundamental contribution of the domain wall in resistivity can be controlled by propagating photon. These results are valuable in designing spintronic devices based on magnetic nanowires.

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Magnetoresistance of non-180° domain wall in the presence of electron-photon interaction

International Nano Letters Magnetoresistance of non-180° domain wall in the presence of electron-photon interaction Roya Majidi 0 0 Department of Physics, Shahid Rajaee Teacher Training University , Lavizan, Tehran 16788-15811 , Iran In the present paper, influence of photon on resistance of non-180° domain wall in metallic magnetic nanowires has been studied using the semiclassical approach. The analysis has been based on the Boltzmann transport equation, within the relaxation time approximation. The one-dimensional Néel-type domain wall between two ferromagnetic domains with relative magnetization angle less than 180° is considered. By increasing this angle, the contribution of the domain wall in the resistivity of the nanowire becomes considerable. It is also found that the fundamental contribution of the domain wall in resistivity can be controlled by propagating photon. These results are valuable in designing spintronic devices based on magnetic nanowires. Magnetoresistance; Non-180° Néel-type domain wall; Metallic nanowire; Magnetization rotation angle; Electron-photon interaction Background Spintronics is an emerging technology with a great promise to provide a new generation of electronic devices where spin of carriers would play a crucial role in addition to or in place of their charge [ 1,2 ]. The design and manufacture of such new spintronic devices require a proper understanding of spin-dependent transport especially in magnetic systems [ 1,2 ]. In recent years, investigating the unique spin transport property and determining the magnetoresistance (MR) of magnetic nanostructures such as nanowires have attracted much attention. Results indicate that MR as a characteristic property of the magnetic nanostructures can be modified significantly by the presence of non-collinear magnetization regions named domain walls (DWs) [ 3 ]. From both scientific and technological points of view, understanding the resistance caused by DWs and determining the effect of different scattering sources on the DW resistance (DWR) are essential. For that reason, many research efforts have been made to understand the role of DW in resistivity [ 4-15 ]. Experiments on iron whiskers demonstrate that DWs are a source of electrical resistance [4]. Contrary to bulk samples, it has been found that the MR associated with nanosize DWs can be significantly large [ 4,5 ]. Theoretically, Levy and Zhang, by studying MR effect due to the magnetic DW scattering, found that the DWs are a source of spin channel mixing and MR enhancement [6]. In addition, investigation of the effect of Rashba spin orbit interaction on the resistance of DW indicates that this interaction causes an increase in the DWR [ 7,8 ]. The temperature dependence of the resistivity of DWs has been also studied. The results clarify that the positive contribution of DWs in increasing the resistivity is enhanced by increasing temperature [ 10-12 ]. In recent years, applying an external magnetic field or propagating a photon to control the DWR has been investigated [ 13-15 ]. It should be mentioned that most of the present studies [ 4-15 ] have focused on the ideal 180° DWs despite the fact that DWs with a magnetization rotation of less than 180° appear in artificial materials [ 16,17 ]. Meanwhile, realization of spintronic devices with improved functionality and performance requires controlling DW configurations and understanding their role in electronic transport. In recent years, contributions of 90°, 180°, and 360° DWs in the resistivity of samples in the presence of external magnetic field are compared [18]. It is found that that resistance of 360° DW is more considerable than that of 90° and 180° DWs. In the present paper, we have studied the influence of photon on the resistivity of the non-180° DW in metallic magnetic nanowires. Methods Theoretical considerations We have studied a metallic magnetic nanowire containing a Néel-type DW. For this DW, the angle between the local direction of the magnetization and the z-axis can be expressed as θ(z) = ϕ z/d, where φ is the magnetization rotation angle of the DW and considered less than 180°. It means that the DW is confined between two magnetic domains with relative magnetization angle of φ, and in such DW, θ changes smoothly from zero to φ over the DW width, d. In Figure 1, the 180° DW with φ = 180° and non180° DW with φ < 180° are shown. The following Hamiltonian has been used to describe the DW in the presence of photon: H ¼ H0 þ Hex þ Hel ph: The first term, H0, contains kinetic energy and nonmagnetic periodic potential. The second term, Hex, represents the exchange interaction between the spin of conduction electrons and the localized magnetic moments. These terms are given by H0 ¼ Hex ¼ ħ2 d2 2m dz2 þ V ðzÞ; Δexσ^:M^ ðzÞ; ð1Þ ð2Þ ð3Þ ð4Þ in which V(z) is the lattice periodic potential, Δex represents the exchange interaction strength, σ^ denotes the Pauli spin matrices, and M^ ðzÞ (...truncated)


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Roya Majidi. Magnetoresistance of non-180° domain wall in the presence of electron-photon interaction, International Nano Letters, 2013, pp. 18, Volume 3, Issue 1, DOI: 10.1186/2228-5326-3-18