Temperature induced single domain–vortex state transition in sub-100nm Fe nanodots

Dumas, Randy K.; Liu, Kai; Li, Changpeng; Roshchin, Igor V.; Schuller, Iván K.

doi:10.1063/1.2807276

Cited by 68 publications

(87 citation statements)

References 23 publications

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“…Hysteresis curves were collected up to 10 kOe in 250 Oe steps. A subset of films were also studied using first-order reversal curves (FORC) [32][33][34] using a MicroMag 2900 vibrating sample magnetometer (Princeton Measurements Corp., Princeton, NJ). …”

Section: B Characterizationmentioning

confidence: 99%

Ion irradiation of Fe-Fe oxide core-shell nanocluster films: Effect of interface on stability of magnetic properties

McCloy

Jiang

Droubay

et al. 2013

Journal of Applied Physics

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A cluster deposition method was used to produce films of loosely aggregated nanoclusters (NC) of Fe core-Fe 3 O 4 shell or fully oxidized Fe 3 O 4 . Films of these NC on Si(100) or MgO(100)/Fe 3 O 4 (100) were irradiated to 10 16 Si 2+ /cm 2 near room temperature using an ion accelerator. Ion irradiation creates structural change in the NC film with corresponding chemical and magnetic changes which depend on the initial oxidation state of the cluster. Films were characterized using magnetometry (hysteresis, first order reversal curves), microscopy (transmission electron, helium ion), and x-ray diffraction. In all cases, the particle sizes increased due to ion irradiation, and when a core of Fe is present, irradiation reduces the oxide shells to lower valent Fe species. These results show that ion irradiated behavior of the nanocluster films depends strongly on the initial nanostructure and chemistry, but in general saturation magnetization decreases slightly.

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Section: B Characterizationmentioning

confidence: 99%

Ion irradiation of Fe-Fe oxide core-shell nanocluster films: Effect of interface on stability of magnetic properties

McCloy

Jiang

Droubay

et al. 2013

Journal of Applied Physics

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“…For example, information on distributions of key magnetic parameters, interactions, and phase identification in a variety of bulk, thin film, and patterned systems has been shown. [16][17][18][19][20][21][22] To date, however, FORC analysis has focused on measurements that encompass the entire magnetic volume. Graded materials, which are explicitly designed to exhibit magnetic properties that vary throughout their thickness, provide a unique opportunity to extend the capabilities of FORC with the surface sensitivity of MOKE.…”

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confidence: 99%

First-order reversal curve analysis of graded anisotropy FePtCu films

Bonanni

Fang

Dumas

et al. 2010

Applied Physics Letters

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The reversal mechanisms of graded anisotropy FePtCu films have been investigated by alternating gradient magnetometer ͑AGM͒ and magneto-optical Kerr effect ͑MOKE͒ measurements with first-order reversal curve ͑FORC͒ techniques. The AGM-FORC analysis, which clearly shows the presence of soft and hard components, is unable to resolve how these phases are distributed throughout the film thickness. MOKE-FORC measurements, which preferentially probe the surface of the film, reveal that the soft components are indeed located toward the top surface. Combining AGM-FORC with the inherent surface sensitivity of MOKE-FORC analysis allows for a comprehensive analysis of heterogeneous systems such as graded materials. © 2010 American Institute of Physics. ͓doi:10.1063/1.3515907͔Graded anisotropy materials 1,2 have joined the ranks of tilted 3,4 and exchange coupled composite 5 ͑ECC͒ recording media as possible solutions to the magnetic recording trilemma, 6,7 where simultaneously balancing the thermal stability and signal-to-noise ratio with the writability of a given bit is necessary. Energy-assisted recording techniques, such as heat-assisted magnetic recording 8 and microwave-assisted magnetic recording, 9 rely on adding energy to the media in order to temporarily surmount the switching barrier with modest applied fields. In graded materials, which are predicted to provide additional gains in writability over conventional bilayer hard/soft ECC media, the anisotropy is systematically varied such that the switching field is reduced by the low anisotropy layers, while the high anisotropy layers preserve thermal stability. There have been few reports, mostly based on rather thick multilayered structures, on the successful creation of graded materials.10-14 However, the realization of a continuous anisotropy gradient was recently achieved in properly annealed compositionally graded thin FePtCu films. 15 In conjunction with the fabrication, the subsequent analysis of graded materials is not trivial and often requires complicated measurement apparatuses. For example, the inherent depth sensitivity of polarized neutron reflectivity measurements has recently been used to directly probe the anisotropy gradient of multilayered Co/Pd samples. 12,13 In this letter, we report on a relatively simple measurement and analysis technique that combines first-order reversal curve ͑FORC͒ 16-22 measurements with the inherent surface sensitivity of the magneto-optical Kerr effect ͑MOKE͒ to analyze FePtCu films with a continuously graded anisotropy. In addition to providing a useful qualitative fingerprint of the magnetization reversal mechanisms, the FORC techniques are able to extract a wealth of quantitative information not readily accessible from standard major loop or remanence curve analysis. For example, information on distributions of key magnetic parameters, interactions, and phase identification in a variety of bulk, thin film, and patterned systems has been shown. [16][17][18][19][20][21][22] To date, however, FORC analysis has focused ...

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“…Magnetization versus field (hysteresis loop to 630 kOe) was collected at 10 K and 77 K after various cooling fields (H FC ) (0, 0.1, 1, 10, and 30 kOe), and loop iterations (4 cycles). First-order reversal curves (FORC) [13][14][15][16] to 615 kOe were measured using a MicroMag 3900 VSM (Princeton Measurements Corp.) at 300 K and at 77 K with zero-field cooling (ZFC) and field cooling (FC) under 1 kOe or 10 kOe (i.e., H FC ¼ 0, 1 kOe, 10 kOe). The measurement starts from positive saturation and involves measuring a series of partial hysteresis curves at progressively more negative reversal field H R under increasing applied field H back to positive saturation.…”

Section: Methodsmentioning

confidence: 99%

Exchange bias in polycrystalline magnetite films made by ion-beam assisted deposition

Kaur

Jiang

Qiang

et al. 2014

Journal of Applied Physics

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Iron oxide films were produced using ion-beam-assisted deposition, and Raman spectroscopy and x-ray diffraction indicate single-phase magnetite. However, incorporation of significant fractions of argon in the films from ion bombardment is evident from chemical analysis, and Fe/O ratios are lower than expected from pure magnetite, suggesting greater than normal disorder. Low temperature magnetometry and first-order reversal curve measurements show strong exchange bias, which likely arises from defects at grain boundaries, possibly amorphous, creating frustrated spins. Since these samples contain grains $6 nm, a large fraction of the material consists of grain boundaries, where spins are highly disordered and reverse independently with external field. V C 2014 AIP Publishing LLC. [http://dx

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Temperature induced single domain–vortex state transition in sub-100nm Fe nanodots

Cited by 68 publications

References 23 publications

Ion irradiation of Fe-Fe oxide core-shell nanocluster films: Effect of interface on stability of magnetic properties

Ion irradiation of Fe-Fe oxide core-shell nanocluster films: Effect of interface on stability of magnetic properties

First-order reversal curve analysis of graded anisotropy FePtCu films

Exchange bias in polycrystalline magnetite films made by ion-beam assisted deposition

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