The roles of the exchange and dipole couplings on the magnetoresistance for the nanoparticle arrays

Yang, Yue; Shen, Shuangjuan; Ye, Qingying; Lin, Liming; Huang, Zhigao

doi:10.1016/j.jmmm.2006.01.233

Cited by 11 publications

(12 citation statements)

References 7 publications

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“…Using micromagnetic simulations, Haase and Nowak reported that magnetic hyperthermia efficiency decreases with an increase in dipolar interaction strength [41]. The dipolar interaction also has a drastic effect on the tunnel magnetoresistance, a useful quantifier for spintronics based applications [42][43][44][45][46]. For example, Tan et al found the detrimental effect of dipolar interaction on the tunnel magnetoresistance in square arrays of MNPs [44].…”

Section: Introductionmentioning

confidence: 99%

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Hysteresis in Two Dimensional Arrays of Magnetic Nanoparticles

Anand

2021

Preprint

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We perform computer simulations to probe the magnetic hysteresis in a two-dimensional (L x ×L y ) assembly of magnetic nanoparticles as a function of dipolar interaction strength h d , temperature T , aspect ratio A r = L y /L x , and the applied alternating magnetic field's direction. In the absence of magnetic interaction (h d ≈ 0) and thermal fluctuations (T = 0 K), the hysteresis follows the Stoner and Wohlfarth model, as expected. For weak dipolar interaction and substantial temperature, the hysteresis has the dominance of superparamagnetic behaviour, irrespective of the applied magnetic field's direction and A r . Interestingly, the hysteresis curve has all the characteristics of antiferromagnetic interaction dominance for A r ≤ 6 and considerable dipolar interaction strength (h d > 0.2), which is independent of applied magnetic direction. When the magnetic field is applied along the system's shorter axis (x-direction), a non-hysteresis straight line is observed with large h d . In the case of the magnetic field applied along the long axis of the sample (y-direction), ferromagnetic interaction dominates the hysteresis for large h d and A r > 6. Irrespective of h d and applied magnetic field's direction, the coercive field µ o H c and remanence M r are minimal for A r ≤ 6 and significant temperature. They are found to increase with h d when A r is enormous.Remarkably, the variation of hysteresis loop area E H as a function of these parameters is the same as that of the coercive field variation. We believe that the concepts presented in this work are relevant in various technological applications such as spintronics and magnetic hyperthermia, in which such self-assembled nanoparticle arrays are ubiquitous.

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Section: Introductionmentioning

confidence: 99%

“…For example, Tan et al found the detrimental effect of dipolar interaction on the tunnel magnetoresistance in square arrays of MNPs [44]. [45,46].…”

Section: Introductionmentioning

confidence: 99%

Hysteresis in Two Dimensional Arrays of Magnetic Nanoparticles

Anand

2021

Preprint

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“…Consequently, the influence of the relevant interparticle interactions, mainly the magnetic dipolar interaction, on these magnetoresistive properties becomes an important issue to clarify. Few numerical investigations have been done by Monte Carlo simulations [28,29] or by solving the LLG equation [30]. However, these works have been focused essentially on restricted types of materials with fixed anisotropy direction or fixed intrinsic parameters such as saturation magnetization and the effective anisotropy constant.…”

Section: Introductionmentioning

confidence: 99%

Numerical simulations of collective magnetic properties and magnetoresistance in 2D ferromagnetic nanoparticle arrays

Tan¹,

Lee²,

Cho³

et al. 2010

J. Phys. D: Appl. Phys.

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Magnetic properties and magnetoresistance (MR) in 2D magnetic nanoparticle (NP) arrays are investigated by solving the Landau–Lifshitz–Gilbert equation at T = 0 K. The interparticle interactions induce a decrease in the coercive field and in the MR amplitude compared with the non-interacting case, while in some cases, the variation of the remanent magnetization is found to be non-monotonic when increasing the dipolar strength. For different values of the anisotropy, these variations of the coercive field, the remanent magnetization and the MR ratio are reproduced and exhibit a scaling on the dipolar/anisotropy ratio. These results suggest that the magnetic properties of the assemblies can be described by an individual or collective behaviour depending on the balance between the magnetic anisotropy and the dipolar interactions. In the case of strongly interacting NPs, the corresponding configurations of the magnetic moments at the remanent state reveal the formation of a ferromagnetic order at moderate dipolar strength (increase in the remanent magnetization) while small ferromagnetic domains/chains coupled antiferromagnetically are obtained in the case of strongly interacting NPs (decrease in the remanent magnetization). Such domains lead to a reduction in the MR amplitude and to a deviation from the m2-law in the resistance-magnetic field [R(H)] characteristic of the non-interacting case.

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“…Kachkachi and Dimian [25], Iglesias and Labarta [26] and Dimitrov and Wysin [27] have studied the influence of surface anisotropy on the hysteretic properties of magnetic nanoparticles. Based on Monte Carlo simulations, Yang et al [28] have studied the roles of the exchange (J ) and dipole (D) couplings on the magnetoresistance for nanoparticles. The simulated results reveal that the coercivity H c increases with decreasing value of D and increasing magnitude of J .…”

Section: Introductionmentioning

confidence: 99%

Size, anisotropy and doping effects on the coercive field of ferromagnetic nanoparticles

Wesselinowa¹,

Apostolova²

2007

J. Phys.: Condens. Matter

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The influence of size, anisotropy and doping effects on the hysteresis loop of ferromagnetic nanoparticles is studied, based on the modified Heisenberg model. A Green's function technique in real space allows the calculation of the dependence of the magnetization on the temperature, magnetic field, anisotropy, defects and particle size. It is demonstrated that the coercive field H(c) is very sensitive to the surface single-ion anisotropy, and to the exchange interaction constant on the surface J(s) and in the defect shells J(d). With respect to the strong surface single-site anisotropy D(s), we observe at small particle size, N = 4 shells, a maximum in the size dependence of the coercive field, whereas for the small surface anisotropy there is no maximum. Taking into account that J can be different in the defect shells compared to the case without defects, we have obtained for the first time that the coercive field H(c), the permanent magnetization M(r) and the Curie temperature T(C) can increase or decrease for different kinds of doping ions. The dependence on the particle size is discussed, too. The results are in accordance with the experimental data.

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The roles of the exchange and dipole couplings on the magnetoresistance for the nanoparticle arrays

Cited by 11 publications

References 7 publications

Hysteresis in Two Dimensional Arrays of Magnetic Nanoparticles

Hysteresis in Two Dimensional Arrays of Magnetic Nanoparticles

Numerical simulations of collective magnetic properties and magnetoresistance in 2D ferromagnetic nanoparticle arrays

Size, anisotropy and doping effects on the coercive field of ferromagnetic nanoparticles

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