Exchange through nonmagnetic insulating matrix

Skomski, Ralph; Kashyap, Arti; Qiang, You; Sellmyer, David J.

doi:10.1063/1.1541633

Cited by 15 publications

(12 citation statements)

References 14 publications

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“…The effective exchange between two grains shows a complicated dependence on factors such as grain separation and size, 11 interface structure, 12 and matrix composition.…”

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confidence: 99%

Structural effects on exchange in nanocluster perpendicular recording media

Zhou

Skomski

Sellmyer

2006

Journal of Applied Physics

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Nanostructured FePt:M (M=C,Ag,Cu) perpendicular magnetic recording media are investigated by numerical simulations and model calculations. Both intra- and intergranular exchanges are considered, and it is assumed that the interaction through the matrix is mediated by conduction electrons. Several limits, including free-electron-like Ruderman-Kittel-Kasuya-Yosida interactions, are considered. The atomic modeling yields effective intergranular coupling strengths that depend on both cluster radius and distance, on the magnetic properties of the clusters, and on the electronic nature of the medium. In the simulations, the exchange is approximated by a thin shell with reduced exchange and zero anisotropy. The simulations show that intergranular exchange reduces the coercivity of the system, and the magnetization reversal proceeds in a regime between localized nucleation and discrete domain-wall pinning, depending on the intergranular exchange. Coercivity and loop-shape reduction also depend on the geometry of the particle system.

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“…The effective exchange between two grains shows a complicated dependence on factors such as grain separation and size, 11 interface structure, 12 and matrix composition.…”

mentioning

confidence: 99%

Structural effects on exchange in nanocluster perpendicular recording media

Zhou

Skomski

Sellmyer

2006

Journal of Applied Physics

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“…͑5͒, and the net effect is usually stronger, as analyzed for magnetic particles in a bulk matrix. 17 Near-contact interactions are actually observed in some of our samples, where they improve the hysteresis-loop squareness. 11 Note that the net RKKY interactions decay more rapidly than dipole interactions and are a small though not necessarily negligible correction for particles larger than about 1 nm.…”

Section: Discussionmentioning

confidence: 99%

Substrate-controlled growth and magnetism of nanosize Fe clusters on Pt

Skomski

Zhang

Sessi

et al. 2008

Journal of Applied Physics

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The growth and magnetism of nanosize Fe clusters on Pt and other metal surfaces are investigated. Fe clusters have been fabricated directly on the substrates by buffer layer assisted growth under ultrahigh vacuum conditions. The mean cluster diameter and the average cluster spacing were controlled by the Fe coverage and the buffer layer thickness. The enhanced magnetic anisotropy of such clusters of diameters between 0.5 and 10 nm with respect to bulk is discussed. Interface anisotropy contributions are compared with direct dipolar cluster-cluster interaction and indirect interactions mediated by the substrate, including preasymptotic ferromagnetic interaction. It is found that this preasymptotic exchange is rather strong in exchange-enhanced substrates, such as Pt, but it decreases rapidly with increasing distance between clusters and becomes negligible for the experimental cluster spacings in this work. Except for clusters that nearly touch each other, the leading interaction contributions are RKKY-type exchange and magnetostatic dipole interactions.

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“…Intergranular exchange, and magnetostatic interactions, modify the coercivity of granular magnets. Atomically, it matters whether the matrix is ferromagnetic, paramagnetic, or insulating [3,12,13], but for small and weakly coupled grains, the exchange can be modeled by a single parameter J. (In general, the calculation of J involves an integration over all exchange paths and differs from what one would expect by counting the surface atoms of adjacent grains.…”

Section: Coherent Rotation and Discrete Pinningmentioning

confidence: 99%