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4 Jul 2005

Volume 87, Issue 1, Articles (01xxxx)

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Appl. Phys. Lett. 87, 013110 (2005); http://dx.doi.org/10.1063/1.1977187 (3 pages)

R. C. Wang, C. P. Liu, J. L. Huang, S.-J. Chen, Y.-K. Tseng, and S.-C. Kung
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Critical size for exchange bias in ferromagnetic-antiferromagnetic particles

A. N. Dobrynin, D. N. Ievlev, K. Temst, P. Lievens, J. Margueritat, J. Gonzalo, C. N. Afonso, S. Q. Zhou, A. Vantomme, E. Piscopiello, and G. Van Tendeloo

Appl. Phys. Lett. 87, 012501 (2005); http://dx.doi.org/10.1063/1.1978977 (3 pages) | Cited 45 times

Online Publication Date: 27 June 2005

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We present a study of the magnetic properties of oxidized Co nanoparticles with an average grain size of 3 nm, embedded in an amorphous Al2O3 matrix. These nanoparticles can be considered as imperfect Co-core CoO-shell systems. Magnetization measurements after magnetic field cooling show a vertical shift of the hysteresis loop, while no exchange bias is observed. With a simple model, we show that there is a critical grain size for hybrid ferromagnetic-antiferromagnetic particles, below which exchange bias is absent for any ratio of ferromagnetic and antiferromagnetic constituents. The reason is that the interfacial exchange energy dominates over other energies in the system due to a large surface-to-volume ratio in the nanoparticles.
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75.50.Tt Fine-particle systems; nanocrystalline materials
75.50.Cc Other ferromagnetic metals and alloys
75.50.Ee Antiferromagnetics
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.30.Sg Magnetocaloric effect, magnetic cooling
75.30.Et Exchange and superexchange interactions
61.46.-w Structure of nanoscale materials
68.35.Md Surface thermodynamics, surface energies

Narrowing of the frequency-linewidth in structured magnetic strips: Experiment and theory

Bijoy Kuanr, R. E. Camley, and Z. Celinski

Appl. Phys. Lett. 87, 012502 (2005); http://dx.doi.org/10.1063/1.1968433 (3 pages) | Cited 17 times

Online Publication Date: 27 June 2005

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We examine the frequency-linewidth in structured magnetic materials experimentally and theoretically and show that this linewidth can decrease as the external field (or the frequency) is increased. This decrease in the frequency-linewidth occurs in many different systems and does not indicate an increase in damping at low frequencies, as has been suggested. Further, the frequency-linewidth can be very large for extended ferromagnetic films, but becomes significantly smaller for structured films that are narrower than a few microns.
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75.70.Ak Magnetic properties of monolayers and thin films
75.50.Bb Fe and its alloys

Magnetoelectric effect of Pb(Zr,Ti)O3 rod arrays in a (Tb,Dy)Fe2/epoxy medium

Z. Shi, C. W. Nan, Jie Zhang, N. Cai, and J.-F. Li

Appl. Phys. Lett. 87, 012503 (2005); http://dx.doi.org/10.1063/1.1991983 (3 pages) | Cited 32 times

Online Publication Date: 29 June 2005

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We report a kind of multiferroic and multifunctional composite with Pb(Zr,Ti)O3 rod arrays embedded in a ferromagnetic medium of (Tb,Dy)Fe2/epoxy. The composite structure is similar to that of 1–3-type piezoelectric composites with Pb(Zr,Ti)O3 rod arrays embedded in an inert epoxy for already commercial applications as transducers. The large magnetoelectric effect, especially at high frequency at which the electromechanical resonance appears, is observed for such multiferroic composites due to coupling elastic interaction between Pb(Zr,Ti)O3 rods and the ferromagnetic medium, which suggests avenues for designing novel multiferroic materials for practical applications.
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77.84.Lf Composite materials
75.50.Bb Fe and its alloys
75.80.+q Magnetomechanical effects, magnetostriction
77.65.Bn Piezoelectric and electrostrictive constants
77.65.Fs Electromechanical resonance; quartz resonators
72.30.+q High-frequency effects; plasma effects

Exchange spring media for perpendicular recording

D. Suess, T. Schrefl, S. Fähler, M. Kirschner, G. Hrkac, F. Dorfbauer, and J. Fidler

Appl. Phys. Lett. 87, 012504 (2005); http://dx.doi.org/10.1063/1.1951053 (3 pages) | Cited 128 times

Online Publication Date: 30 June 2005

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A novel type of exchange spring media is proposed for magnetic recording systems consisting of a hard/soft bilayer. Finite element micromagnetic simulations show that the reversal modes induced by the external write field are significantly different from the thermally activated switching processes. Thus, the bilayers can be optimized in order to achieve a high thermal stability without increase of coercive field. In grains with identical size and coercivity an optimized bilayer reaches an energy barrier exceeding those of optimized single phase media by more than a factor of two. Additionally the lower angular dependence of coercivity of exchange spring media will improve the signal to noise ratio.
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75.50.Ss Magnetic recording materials
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

High magnetoresistive sensitivity in electrodeposited FeCoNi/Cu multilayers

Jie Gong, William H. Butler, and Giovanni Zangari

Appl. Phys. Lett. 87, 012505 (2005); http://dx.doi.org/10.1063/1.1952573 (3 pages) | Cited 5 times

Online Publication Date: 30 June 2005

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FeCoNi/Cu multilayers with large magnetoresistive sensitivity at low field have been electrodeposited on n-type Si from a single electrolyte by modulating the deposition potential. Dissolution of the ferromagnetic (FM) layer during copper deposition was minimized and interface sharpness was improved by monitoring the current transients during the transition from FM to Cu deposition and using these data to fine tune the Cu deposition potential and Fe2+ concentration in the electrolyte. Using optimal processing parameters, a maximum giant magnetoresistance (GMR) ratio above 9% could be obtained. Maximum GMR sensitivity of over 0.11%/Oe was achieved in the field range 5–15 Oe.
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75.50.Bb Fe and its alloys
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.47.De Giant magnetoresistance
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