Magnetic relaxation of nanowires: beyond the Néel-Brown activation process

Wegrowe, J.-E.; Meier, J.; Doudin, B.; Ansermet, Jean-Philippe; Wernsdorfer, Wolfgang; Barbara, B.; Coffey, W. T.; Kalmykov, Yuri P.; Déjardin, Jean‐Louis

doi:10.1209/epl/i1997-00247-9

Cited by 18 publications

(13 citation statements)

References 18 publications

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“…Although disorder can modify the relaxation behavior, systems with strong residual interaction between neighboring domains exhibit slow, logarithmic relaxation (23). Relaxation processes with time scale comparable to our system are found in spin glasses (29) and low-dimensional ferromagnets (30)(31)(32). Aspects of relaxation such as randomness of local spin configurations and broad distribution of relevant energy scales are common between these systems.…”

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confidence: 54%

Quantum Hall Ferromagnetism in a Two-Dimensional Electron System

Eom

Cho

Kang

et al. 2000

Science

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Experiments on a nearly spin degenerate two-dimensional electron system reveals unusual hysteretic and relaxational transport in the fractional quantum Hall effect regime. The transition between the spin-polarized (with fill fraction nu = 1/3) and spin-unpolarized (nu = 2/5) states is accompanied by a complicated series of hysteresis loops reminiscent of a classical ferromagnet. In correlation with the hysteresis, magnetoresistance can either grow or decay logarithmically in time with remarkable persistence and does not saturate. In contrast to the established models of relaxation, the relaxation rate exhibits an anomalous divergence as temperature is reduced. These results indicate the presence of novel two-dimensional ferromagnetism with a complicated magnetic domain dynamic.

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confidence: 54%

Quantum Hall Ferromagnetism in a Two-Dimensional Electron System

Eom

Cho

Kang

et al. 2000

Science

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“…The magnetic irreversibility in nanoparticles is conventionally associated with the energy required for a particle moment reorientation, overcoming a barrier due to magnetic shape or crystalline anisotropy. It is important to note that the barrier is considered to be independent of the magnetic moment itself 8,10,[17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32] . In superconductors, magnetic irreversibility is due to the inevitable spatial fluctuation of the superconducting order parameter caused by defects, imperfections etc.…”

Section: Introductionmentioning

confidence: 99%

Magnetic irreversibility and relaxation in assembly of ferromagnetic nanoparticles

et al. 1999

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Measurements of the magnetic irreversibility line and time-logarithmic decay of the magnetization are described for three F e2O3 samples composed of regular amorphous, acicular amorphous and crystalline nanoparticles. The relaxation rate is the largest and the irreversibility temperature is the lowest for the regular amorphous nanoparticles. The crystalline material exhibits the lowest relaxation rate and the largest irreversibility temperature. We develop a phenomenological model to explain the details of the experimental results. The main new aspect of the model is the dependence of the barrier for magnetic relaxation on the instantaneous magnetization and therefore on time. The time dependent barrier yields a natural explanation to the time-logarithmic decay of the magnetization. Interactions between particles as well as shape and crystalline magnetic anisotropies define a new energy scale that controls the magnetic irreversibility. Introducing this energy scale yields a self-consistent explanation of the experimental data.

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“…Samples with contacts to several nanowires ͑not shown͒ present several jumps, as the switching field is known to have a wide distribution. 27 Wires of diameters over 150 nm, instead, were found to depart clearly from a single domain behavior ͑Fig. 2͒.…”

Section: Samplesmentioning

confidence: 99%

Real time probing of magnetization switching in magnetic nanostructures

Guittienne

Gravier

Wegrowe

et al. 2002

Journal of Applied Physics

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Time-resolved anisotropic magnetoresistance ͑AMR͒ measurements of the irreversible switching of the magnetization were performed on isolated Ni nanowires. The magnetization reversal was triggered by injection of high current densities in a static magnetic field. The detection was achieved by means of a Wheatstone bridge with a 1 GHz bandwidth. Time-resolved switching was obtained in single shot measurements. Nanowires with diameter of about 100 nm that present a uniform rotation in the reversible regime detected in quasistatic AMR measurements are found to have switching in about 14 ns. This value can be accounted for in the framework of an uniform rotation model with value of the Gilbert damping coefficient of 0.005-0.01. Nanowires with larger diameters ͑typ. 200 nm͒ that manifest inhomogeneous magnetization in quasistatic AMR measurements have a switching time of about 37 ns.

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Magnetic relaxation of nanowires: beyond the Néel-Brown activation process

Cited by 18 publications

References 18 publications

Quantum Hall Ferromagnetism in a Two-Dimensional Electron System

Quantum Hall Ferromagnetism in a Two-Dimensional Electron System

Magnetic irreversibility and relaxation in assembly of ferromagnetic nanoparticles

Real time probing of magnetization switching in magnetic nanostructures

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