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Spontaneous Domain Wall Motion at Zero External Magnetic Field in Ferromagnetic Nanowire
Djuhana, D.,Hong-Guang Piao,Je-Ho Shim,Sang-Hyuk Lee,Su-Hyeong Jun,Seong-Cho Yu,Suhk Kun Oh,Dong-Hyun Kim IEEE 2010 IEEE transactions on magnetics Vol.46 No.2
<P>We have explored a spontaneous domain wall motion in ferromagnetic nanowire at zero external magnetic field by means of micromagnetic simulation. Very interestingly, even with no external magnetic field, a spontaneous domain wall motion is observed with a speed about few tens of m/s, which is significant and not negligible in analysis of the domain wall dynamics on nanowires. The spontaneous zero-field wall motion is explained based on the minimization condition of the magnetostatic energy, preferring to have a wire magnetically saturated. Average speed of the spontaneous wall motion is found to increase as the wire thickness increases.</P>
D. Djuhana,L. Rohman,D. H. Kim 한국자기학회 2017 Journal of Magnetics Vol.22 No.3
In this study, we have systematically calculated the dynamic susceptibility spectra of LSMO (La0.7Sr0.3MnO₃) ferromagnetic nanopillars by means of a micromagnetic simulation. Simulation has been carried out for LSMO nanopillars consisted of disk and square shapes with respect to the height variation. The diameter of disk pillar and the length of square pillar were fixed to be 50 nm and the height of pillar were varied from 100 to 500 nm with increment of 50 nm. The exponential type magnetic pulses have been applied in the long axis and perpendicular to the initial spin configuration of the pillars. The dynamic susceptibility spectra of the pillar were determined by fast Fourier transform (FFT) based on the magnetization response. We have obtained the resonance frequency of the pillars from the imaginary part of the dynamic susceptibility spectra. Interestingly, the resonance frequency peak of the nanopillars increased as the height increased and followed the Kittel’s resonance formula. It was found that the demagnetization energy from dipolar interaction mainly contributed to the frequency resonance of the nanopillars.
Sri Budiawanti,R. Amalia,D. T. Rahardjo,Suharno,B. Purnama,D. Djuhana 한국자기학회 2022 Journal of Magnetics Vol.27 No.1
We prepared and characterized nickel-substituted cobalt ferrite (Ni0.1Co0.9Fe₂O₄) nanoparticles using the sol-gel method. The physical properties of the nanoparticles have been modified by postannealing treatment at atmospheric conditions. X-ray diffraction results confirmed that the nanoparticles possessed a single-phase face-centered cubic crystalline structure. The crystallite sizes increased from 20.85 to 26.06 nm with the increased annealing temperature. Transmission electron microscopy results confirmed the crystal structure of the nickel-substituted cobalt ferrite nanoparticles. Furthermore, Fourier-transform infrared spectroscopy results showed that the typical characteristic absorption of the nanoparticles was obtained at wave numbers k = 575 and 374 cm<SUP>−1</SUP>. Finally, the saturation magnetization and coercivity of the nanoparticles increased with the annealing temperature, which is attributed to the increase in magnetic anisotropy constant.
Three-dimensional spin configuration of ferromagnetic nanocubes.
Piao, H-G,Djuhana, D,Shim, J-H,Lee, S-H,Jun, S-H,Oh, S K,Yu, S-C,Kim, D-H American Scientific Publishers 2010 Journal of Nanoscience and Nanotechnology Vol.10 No.11
<P>We have systematically investigated three-dimensional spin configurations in ferromagnetic nanocubes using micromagnetic simulation with variation of cube geometry. For thin cuboids, a spin configuration exhibits a four-domain Landau state with a magnetic vortex structure at the center as in the case of a thin film square. For a thick cube, a complex spin configuration with an S-type cylindrically asymmetric vortex having two cores on a pair of surfaces while a leaf-like and a C-type states are observed on the other two pairs of cube surfaces. Competition between the geometrical symmetry and magnetic energy minimization condition in ferromagnetic nanocubes leads to the complex spin structure with a spontaneously broken symmetry.</P>
Piao, H.-G.,Shim, J.-H.,Djuhana, D.,Lee, S.-H.,Jun, S.-H.,Heo, C.-M.,Oh, S.-K.,Yu, S.-C.,Kim, D.-H. IEEE 2010 IEEE transactions on magnetics Vol.46 No.2
<P>We have investigated a damped oscillatory behavior of domain wall propagation in wavy nanowires under an external field higher than the Walker breakdown field using micromagnetic simulation. In nanowires having sinusoidal edge distortions with variation of wavelengths, domain wall has been observed to pseudomorphically follow the sinusoidal wires with keeping an intrinsic transformational frequency of inner wall spin structure. Oscillation amplitude of the domain wall position decreases as the wavelength of the wire decreases by an interaction between the periodically distributed spins and the propagating domain wall. Oscillatory behavior of the domain wall position is found to decay in a wire having the wavelength well matching with an intrinsic transformational frequency of the propagating domain wall.</P>
Domain Wall Propagation in Wavy Ferromagnetic Nanowire
Piao, H.-G.,Shim, J.-H.,Lee, S.-H.,Djuhana, D.,Oh, S.-K.,Yu, S.-C.,Kim, D.-H. IEEE 2009 IEEE transactions on magnetics Vol.45 No.10
<P>We have investigated magnetic domain wall propagation behavior in wavy nanowires using micromagnetic simulation. The wire width is set to have sinusoidal distortion with variation of spatial frequency and phase. We have analyzed domain wall speed under a constant external field with variation of wavy geometry. Interestingly, with introduction of proper wavy geometry, domain wall speed becomes faster than the speed of domain wall in a straight wire, where a periodic change of domain wall inner structure has been observed with suppression of vortex structure formation.</P>