Fabrication, Magnetic, and R/W Properties of Nitrogen-Ion-Implanted Co/Pd and CoCrPt Bit-Patterned Medium

Ajan, Antony; Satô, Kenji; Aoyama, Nobuhide; Tanaka, Tsutomu; Miyaguchi, Yusuke; Tsumagari, Kanako; Morita, Tadashi; Nishihashi, Tsutomu; Tanaka, Atsushi; Uzumaki, Takuya

doi:10.1109/tmag.2010.2043647

Cited by 16 publications

(4 citation statements)

References 17 publications

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“…Ion irradiation can thereby avoid the lethal side effects of conventional patterning, in particular for a few nm-thick pillar patterns. Various ferromagnetic metallic systems, such as Co/Pt, Co/Pd, CoCrPt/Cr superlattices, FeAl, and CrPt 3 , with ion sources such as He, Ar, Ga, and Xe in the energy range of 10s keV ∼ 10s MeV have been explored with successful results in magnetic nanopatterning. − Local destruction of an interfacial structure or a crystal structure in an atomic short-range-order by bombardment with accelerated ions has been a fundamental mechanism to achieve such patterning. However, unavoidable drawbacks of this method are (1) unwanted defect formations due to high energy or heavy ion bombardments; ,,, (2) cross-talk or exchange coupling between patterns through the unpatterned ferromagnetic medium, which results in a loss of control over magnetic switching; and (3) limitations in the use of various material systems such as oxides, nitrides, and sulfides.…”

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confidence: 99%

An Array of Ferromagnetic Nanoislands Nondestructively Patterned via a Local Phase Transformation by Low-Energy Proton Irradiation

2014

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Low-energy proton irradiation was applied to pattern an array of metallic, ferromagnetic nanoislands through the local phase transformation of an oxidic, paramagnetic phase in a complex superlattice composed of repetitions of an oxidic and metallic layer. The irradiation inflicted minimal damage on the structure, resulting in the absence of unwanted defects and side effects. This nondestructive pattern transfer was clearly confirmed by the contrast between irradiated and unirradiated regions in electrical, chemical, and magnetic images. Simulation based on the magnetic properties suggests that this low-energy proton irradiation can nondestructively pattern an array of ferromagnetic islands with 8.2 nm in diameter and 7.4 nm in spacing between islands, which means it can achieve an areal density of ∼3 Tb/in.(2) with a thermal stability of over 80 kBT. Such an array is strong enough to overcome the so-called superparamagnetism limit in magnetic recording. The attributes demonstrated here corroborate that proton irradiation can be applied to design and pattern devices on a nanometer scale not only for magnetic but also for electric and optical materials systems in all such systems in which a local phase transformation is available.

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An Array of Ferromagnetic Nanoislands Nondestructively Patterned via a Local Phase Transformation by Low-Energy Proton Irradiation

2014

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“…It is therefore crucial to conclusively ensure that bits are exchange decoupled using the simplest possible approaches. However, existing methods for testing the patterned bits either require elaborate full-system tests with read-write routines [7][8][9] or rely on measurements that either provide qualitative analysis [10][11][12][13][14] or work only with exchange-decoupled bits [15,16]. Furthermore, using a single test could in some instances not bring out exchange-coupled behavior, causing a false indication of isolated bits.…”

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confidence: 99%

A facile approach for screening isolated nanomagnetic behavior for bit-patterned media

Thiyagarajah¹,

Asbahi²,

Wong³

et al. 2014

Nanotechnology

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Bit-patterned media (BPM) fabricated by the direct deposition of magnetic material onto prepatterned arrays of nanopillars is a promising approach for increasing magnetic recording of areal density. One of the key challenges of this approach is to identify and control the magnetic interaction between the bits (on top of the nanopillars) and the trench material between the pillars. Using independent techniques, including magnetic force microscopy, the variable-angle magneto-optic Kerr effect, and remanence curves, we were able to determine the presence and relative intensities of exchange and dipolar interactions in Co-Pd multilayer-based BPM fabricated by direct deposition. We found that for pitches of 30 nm or less, there were negligible exchange interactions, and the bits were found to be magnetically isolated. As we move to higher densities, the absence of exchange interactions indicates that direct deposition is a promising approach to BPM fabrication.

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“…A Co/Pd multilayer is a good candidate for graded media because its magnetic anisotropy is tunable by varying parameters such as the Co and Pd layer thicknesses, the number of repeats, the sputtering conditions [6] and the ion irradiation [7][8][9]. In particular, the irradiation of Co/Pd multilayers monotonically reduces the perpendicular magnetic anisotropy.…”

Section: Introductionmentioning

confidence: 99%

Graded bit patterned magnetic arrays fabricated via angled low-energy He ion irradiation

Chang¹,

Nasruallah²,

Ruchhoeft³

et al. 2012

Nanotechnology

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A bit patterned magnetic array based on Co/Pd magnetic multilayers with a binary perpendicular magnetic anisotropy distribution was fabricated. The binary anisotropy distribution was attained through angled helium ion irradiation of a bit edge using hydrogen silsesquioxane (HSQ) resist as an ion stopping layer to protect the rest of the bit. The viability of this technique was explored numerically and evaluated through magnetic measurements of the prepared bit patterned magnetic array. The resulting graded bit patterned magnetic array showed a 35% reduction in coercivity and a 9% narrowing of the standard deviation of the switching field.

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Fabrication, Magnetic, and R/W Properties of Nitrogen-Ion-Implanted Co/Pd and CoCrPt Bit-Patterned Medium

Cited by 16 publications

References 17 publications

An Array of Ferromagnetic Nanoislands Nondestructively Patterned via a Local Phase Transformation by Low-Energy Proton Irradiation

An Array of Ferromagnetic Nanoislands Nondestructively Patterned via a Local Phase Transformation by Low-Energy Proton Irradiation

A facile approach for screening isolated nanomagnetic behavior for bit-patterned media

Graded bit patterned magnetic arrays fabricated via angled low-energy He ion irradiation

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