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12 Apr 2004

Volume 84, Issue 15, pp. 2721-2955

Issue Cover Spotlight Figure

Appl. Phys. Lett. 84, 2883 (2004); http://dx.doi.org/10.1063/1.1702137 (3 pages)

Pu Xian Gao and Zhong L. Wang
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Magnetic phase diagram of two identical coupled nanomagnets

D. C. Worledge

Appl. Phys. Lett. 84, 2847 (2004); http://dx.doi.org/10.1063/1.1695632 (3 pages) | Cited 48 times

Online Publication Date: 7 April 2004

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The theoretical magnetic phase diagram of two identical nanomagnets is presented. The nanomagnets are assumed to be single domains in the shape of very flat ellipsoids, in order to approximate technologically relevant thin-film samples patterned into ellipses. The phase diagram is organized by type of easy axis hysteresis loop and takes into account, using exact closed analytic expressions, the effect of thickness, width, length, magnetization, and uniaxial intrinsic anisotropy of the two nanoparticles, and exchange coupling between the two particles. Two phase diagrams are presented for the two cases where the intrinsic anisotropy is parallel to either the long or short in-plane axis of the nanoparticles. Complete descriptions of all hysteresis loops and exact analytic formulas for all switching fields are given. © 2004 American Institute of Physics.
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75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.70.Kw Domain structure (including magnetic bubbles and vortices)
75.70.Ak Magnetic properties of monolayers and thin films
75.50.Tt Fine-particle systems; nanocrystalline materials
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.40.Cx Static properties (order parameter, static susceptibility, heat capacities, critical exponents, etc.)
75.30.Gw Magnetic anisotropy
75.40.Mg Numerical simulation studies

Fe- and Ni-doped TiO2 thin films grown on LaAlO3 and SrTiO3 substrates by laser ablation

Nguyen Hoa Hong, W. Prellier, Joe Sakai, and Awatef Hassini

Appl. Phys. Lett. 84, 2850 (2004); http://dx.doi.org/10.1063/1.1695103 (3 pages) | Cited 32 times

Online Publication Date: 7 April 2004

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Room temperature ferromagnetic Fe- and Ni-doped TiO2 thin films were grown by the laser ablation on both LaAlO3 and SrTiO3 substrates. Most of the films are pure anatase, and only the films of Ni content of 3.6% and 4.6% are rutile. Films on LaAlO3 substrates are more crystallized than films on SrTiO3 substrates resulting from the lattice mismatch. Our magnetic measurements also suggest that the ferromagnetism in Fe/Ni:TiO2 films is not due to Fe/Ni segregations but due to Fe/Ni:TiO2 matrices. © 2004 American Institute of Physics.
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75.50.Dd Nonmetallic ferromagnetic materials
68.55.A- Nucleation and growth
75.70.Ak Magnetic properties of monolayers and thin films
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
61.72.S- Impurities in crystals
64.70.K- Solid-solid transitions
81.30.Mh Solid-phase precipitation
81.15.Fg Pulsed laser ablation deposition
75.50.Pp Magnetic semiconductors

Magnetic patterning of exchange-coupled multilayers

Vladislav E. Demidov, Dmitry I. Kholin, Sergej O. Demokritov, Burkard Hillebrands, Frederik Wegelin, and Jan Marien

Appl. Phys. Lett. 84, 2853 (2004); http://dx.doi.org/10.1063/1.1699475 (3 pages) | Cited 12 times

Online Publication Date: 7 April 2004

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The local modification of antiferromagnetic (AF) interlayer exchange coupling by focused ion-beam irradiation has been studied experimentally in the epitaxial Fe/Cr/Fe(001) trilayer systems. Square ferromagnetic (FM) areas of 200×200 μm2 were created in the initially AF trilayer by ion irradiation with a fluence of 1015 ions/cm2. It was found, that in the range of the external magnetic field of about ±200 Oe, the change of magnetic properties at the boundaries separating FM and AF areas occurs within distances of less than 200 nm. This fact allows the use of the technique for magnetic patterning of antiferromagnetically coupled trilayers on the submicrometer scale. © 2004 American Institute of Physics.
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75.50.Ee Antiferromagnetics
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.30.Et Exchange and superexchange interactions
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
61.80.Jh Ion radiation effects
68.35.Ct Interface structure and roughness
68.37.Ps Atomic force microscopy (AFM)
68.37.Rt Magnetic force microscopy (MFM)

Observation of room-temperature magnetoelectric coupling in pulsed-laser-deposited Bi0.6Tb0.3La0.1FeO3 thin films

V. R. Palkar, K. Ganesh Kumara, and S. K. Malik

Appl. Phys. Lett. 84, 2856 (2004); http://dx.doi.org/10.1063/1.1695204 (3 pages) | Cited 38 times

Online Publication Date: 7 April 2004

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Magnetoelectrics, characterized by simultaneous ferroelectric and magnetic ordering, have potential applications in information storage, sensors, etc. However, there are very few materials exhibiting the coexistence of ferroelectric and ferromagnetic ordering at room temperature. Hence, in normal practice, desired magnetoelectric effect is achieved by growing heterostructures of ferroelectric and magnetic materials. Realization of heterostructures with desired properties is not only difficult but also involves complicated lengthy procedures. BiFeO3 is weakly ferroelectric and antiferromagnetic at and above room temperature. We have been successful in enhancing both the ferroelectric and the magnetic properties of BiFeO3 by partial substitution of Tb at Bi site. Thin films of Bi0.6Tb0.3La0.1FeO3, integrated on Si/SiO2/TiO2/Pt substrate by using pulsed laser deposition technique, show good ferroelectric and magnetic properties and also coupling between them. Single step growth of thin films with desired magnetoelectric properties is certainly a cost effective, reliable, and simple alternative to heterostructures. © 2004 American Institute of Physics.
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77.55.-g Dielectric thin films
75.80.+q Magnetomechanical effects, magnetostriction
77.80.Dj Domain structure; hysteresis
75.70.Ak Magnetic properties of monolayers and thin films
81.15.Fg Pulsed laser ablation deposition
68.55.A- Nucleation and growth

Superconducting properties of the 18 K phase in yttrium sesquicarbide system

T. Nakane, T. Mochiku, H. Kito, J. Itoh, M. Nagao, H. Kumakura, and Y. Takano

Appl. Phys. Lett. 84, 2859 (2004); http://dx.doi.org/10.1063/1.1702132 (3 pages) | Cited 12 times

Online Publication Date: 7 April 2004

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The metastable phase of an yttrium sesquicarbide compound, which was recently reported as having a superconductive phase with a Tc of 18 K (18 K phase), was prepared under high pressure from the nominal composition of Y2C3 and Y2C2.9B0.1 in order to investigate this phase. We have succeeded in reproduction, and in the transport measurement for this 18 K phase. It is considered that the reason for the higher Tc than the 11.5 K reported previously is not the small amount of B as the impurity element from the BN crucible. The Bc2 at 0 K estimated from the resistivity data for the 18 K phase seems to be over 30 T. It means that the Tc and the Bc2 of the 18 K phase are as high as those of the general A15-type intermetallic compounds. © 2004 American Institute of Physics.
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74.10.+v Occurrence, potential candidates
74.25.F- Transport properties
74.25.Ha Magnetic properties including vortex structures and related phenomena
74.70.Ad Metals; alloys and binary compounds (including A15, MgB2, etc.)
75.30.Cr Saturation moments and magnetic susceptibilities

Spiral exchange interaction in diluted magnetic semiconductor junction

Shih-Jye Sun, Song-Shien Cheng, and Hsiu-Hau Lin

Appl. Phys. Lett. 84, 2862 (2004); http://dx.doi.org/10.1063/1.1705725 (3 pages) | Cited 4 times

Online Publication Date: 7 April 2004

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We studied the exchange interactions mediated by polarized itinerant carriers in diluted magnetic semiconductor (DMS) junction. In contrast to the ordinary Ruderman–Kittel–Kasuya–Yosida oscillations, the induced moment possesses an interesting spiral motion, accompanied by angular oscillations. The spiral motion remains robust in the entire T<Tc regime while the oscillatory motion gets enhanced as T→Tc. To explore the phenomena, it is proposed that a ferromagnet/DMS/ferromagnet junction would bring out interesting spin-dependent transport properties and possible applications in spintronics. © 2004 American Institute of Physics.
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75.50.Pp Magnetic semiconductors
75.30.Et Exchange and superexchange interactions
72.25.Rb Spin relaxation and scattering
75.30.Cr Saturation moments and magnetic susceptibilities
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
72.25.Dc Spin polarized transport in semiconductors

In situ magnetoresistance of Ni nanocontacts

C.-S. Yang, C. Zhang, J. Redepenning, and B. Doudin

Appl. Phys. Lett. 84, 2865 (2004); http://dx.doi.org/10.1063/1.1705723 (3 pages) | Cited 18 times

Online Publication Date: 7 April 2004

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Magnetoresistance properties of Ni nanocontacts in the ballistic quantum regime are investigated in situ during closure and opening of electrochemically grown planar electrodes. The magnitude of conductance change when sweeping the magnetic field is of the order of the quantum conductance e2/h for conductance values spanning 1–100 quanta. The relative orientation of electric current and applied magnetic field changes the magnetoresistance sign, with symmetry properties reminiscent of bulk anisotropy magnetoresistance. Ex situ investigations of samples of higher conductance values, of the order of 1000 quanta, unambiguously show the analogy with bulk anisotropy magnetoresistance. © 2004 American Institute of Physics.
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75.50.Cc Other ferromagnetic metals and alloys
72.15.Gd Galvanomagnetic and other magnetotransport effects
73.63.Rt Nanoscale contacts
75.30.Gw Magnetic anisotropy
82.45.Fk Electrodes
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