Probing submicron nanomagnets by magneto-optics

Cowburn, R. P.; Koltsov, Denis; Adeyeye, A. O.; Welland, Mark E.

doi:10.1063/1.122945

Cited by 75 publications

(31 citation statements)

References 18 publications

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“…[11][12][13][14][15] Nondestructive methods of detection of magnetic properties especially from confined magnetic structures and surfaces of thin films and the development of magneto-optical data storage have made the magneto-optical detection methods ͓magneto-optic Kerr effect ͑MOKE͔͒ very popular. [16][17][18][19] The static 20 and time-resolved [13][14][15] MOKE investigations of nanomagnets have made use of array measurements due to the enhancement of the total MOKE signal from a large number of elements in an array falling within the area of a diffraction limited laser spot ͑ϳ1 m͒. However, in doing so the intrinsic properties of the individual nanomagnet are not measured and instead a collective response is detected.…”

Section: Introductionmentioning

confidence: 99%

Dynamic dephasing of magnetization precession in arrays of thin magnetic elements

Barman

2009

Phys. Rev. B

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We present a systematic micromagnetic simulation to demonstrate how the static and dynamic behaviors of single nanomagnets are modified in an array. We examine the precessional frequency and damping as a function of the width to separation ͑w / s͒ ratio in arrays of square and circular magnetic elements and compare it with the single nanomagnet dynamics. Both frequency and damping are significantly modified by the interelement interaction. The precessional frequency shows a general trend of increase with w / s ratio due to the increase in the dipolar magnetic field in the array and split into multiple modes when the w / s ratio becomes greater than 1. The damping of precession increases with increase in w / s ratio, i.e., with decrease in the separation between the elements. The increase in damping is found to be due to the mutual dephasing of precession of elements in an array. For larger square nanomagnets, ͑width= 150 nm, thickness= 50 nm͒, where the single nanomagnet dynamics is inherently nonuniform, the effect of the array only increases the incoherence in the precession. For larger circular nanomagnets, ͑width= 150 nm, thickness= 50 nm͒, where the single nanomagnet shows slow vortex core oscillation, the array modifies the dynamics into incoherent spin-wave dynamics whose coherence increases with the increase in w / s ratio. Analysis of static and dynamic magnetic images reveals that the dynamics is strongly dependent on the static magnetization in the arrays. The results presented here show that the dynamics of arrays of nanomagnets is significantly or entirely different from that of individual elements, and hence measurements from arrays may not be considered as the single nanomagnet dynamics. We also evaluate the role of dynamic dephasing in the increased damping coefficient.

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Section: Introductionmentioning

confidence: 99%

Dynamic dephasing of magnetization precession in arrays of thin magnetic elements

Barman

2009

Phys. Rev. B

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“…On the other hand, the magneto-optical Kerr effect ͑MOKE͒ has been utilized to characterize dynamic properties such as the activation volume and the hysteresis loop by using either a focused laser beam or an optical microscope equipped with a charge-coupled device ͑CCD͒ camera. [15][16][17] However, these measurement techniques basically focused on the whole area of a film or a single local area of the patterned sample.…”

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confidence: 99%

Direct observation of non-Gaussian distribution of local magnetic properties in ferromagnetic thin films

Choe

Shin

2002

Phys. Rev. B

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We report our experimental finding that magnetic properties of Co-based multilayer films are shown to exhibit their local variations far from the Gaussian ͑or Lorentzian͒ distribution which are usually assumed. The local variations of the coercivity and the field dependence (ϭϪ‫ץ‬ln /‫ץ‬H) were determined from measurements of the hysteresis loop and the field-dependent switching time , respectively, on spatially resolved local regions 400 nm in size by means of a magneto-optical microscope magnetometer. We show that the two local magnetic properties inversely correlate with each other and a thermally activated process takes place during magnetization reversal on a submicrometer scale in ferromagnetic thin films.In general, the magnetic properties of ferromagnetic thin films are spatially inhomogeneous because of structural and/or chemical imperfections inevitably introduced in the film preparation process. [1][2][3][4] Due to the lack of available techniques capable of providing detailed information about the variations with a high spatial resolution, the variations are typically considered under an assumption of the Gaussian ͑or Lorentzian͒ distribution in most theoretical approachesfor instance, Preisach and micromagnetic modeling. 4 -6 However, there is no clear physical reason for this. The question on the variations in real films is fundamentally important for exploring a realistic model of the magnetic domain configuration and reversal dynamics, which are known to be sensitive to local magnetic properties as evidenced from recent observations-for instance, for Co films grown on Au͑111͒, 1 Pt/Co/Pt͑111͒ trilayers, 2 and Co/Pd multilayers. 3 It is also a crucial technological issue in achieving a high performance of magnetic information technology, 7-9 in which the information is stored in the form of magnetic domains.Versatile experimental techniques including magnetic force microscopy ͑MFM͒, 10 scanning electron microscopy with polarization analysis ͑SEMPA͒, 11 spin-polarized lowenergy electron microscopy ͑SPLEEM͒, 12 near-field scanning optical microscopy ͑NSOM͒, 13 and spin-polarized scanning tunneling microscopy ͑SPSTM͒ ͑Ref. 14͒ have been developed to investigate microscopic domain structures with a spatial resolution of some tens of nanometers. But despite the high spatial resolution of these techniques, quantitative measurements of the local magnetic properties relating to domain reversal behavior have not yet been developed because of limitations imposed by the impossibility of applying a magnetic field and/or slow data acquisition time. On the other hand, the magneto-optical Kerr effect ͑MOKE͒ has been utilized to characterize dynamic properties such as the activation volume and the hysteresis loop by using either a focused laser beam or an optical microscope equipped with a charge-coupled device ͑CCD͒ camera. 15-17 However, these measurement techniques basically focused on the whole area of a film or a single local area of the patterned sample.Hence, to date simultaneous local probing of the magnet...

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“…Hysteresis loop measurements of the dot arrays were carried out using a high sensitivity MOKE. 13,14 Here the average switching behavior of the dots under the laser spot, an elliptical area with short axis length of 5 m, is measured and magnetic fields of up to 400 Oe, oriented parallel to the array edge as shown in Fig. 1, were applied.…”

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confidence: 99%

Arrays of nanoscale magnetic dots: Fabrication by x-ray interference lithography and characterization

Heyderman

Solak

Dávid

et al. 2004

Applied Physics Letters

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Probing submicron nanomagnets by magneto-optics

Cited by 75 publications

References 18 publications

Dynamic dephasing of magnetization precession in arrays of thin magnetic elements

Dynamic dephasing of magnetization precession in arrays of thin magnetic elements

Direct observation of non-Gaussian distribution of local magnetic properties in ferromagnetic thin films

Arrays of nanoscale magnetic dots: Fabrication by x-ray interference lithography and characterization

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