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26 May 2003

Volume 82, Issue 21, pp. 3587-3793

Issue Cover Spotlight Figure

Appl. Phys. Lett. 82, 3716 (2003); http://dx.doi.org/10.1063/1.1577808 (3 pages)

V. Novosad, M. Grimsditch, J. Darrouzet, J. Pearson, S. D. Bader, V. Metlushko, K. Guslienko, Y. Otani, H. Shima, and K. Fukamichi
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Magnetic domain structure in a ferromagnetic shape memory alloy Ni51Fe22Ga27 studied by electron holography and Lorentz microscopy

Y. Murakami, D. Shindo, K. Oikawa, R. Kainuma, and K. Ishida

Appl. Phys. Lett. 82, 3695 (2003); http://dx.doi.org/10.1063/1.1578516 (3 pages) | Cited 34 times

Online Publication Date: 20 May 2003

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Behaviors of magnetic domains with cooling in a Ni51Fe22Ga27 ferromagnetic shape memory alloy were examined by electron holography and Lorentz microscopy. A peculiar meshy pattern was observed in the Lorentz microscope image of the parent phase, being concurrent with the anomaly in the thermomagnetization curve. The meshy pattern was found to stem from the heavily bent lines of magnetic flux. The dramatic change in the magnetic domains is presumably due to some intrinsic magnetic instability that is pronounced by cooling, rather than a phenomenon triggered by the lattice modulation as the precursor effect of martensitic transformations or formation of the intermediate phase as observed in other systems. © 2003 American Institute of Physics.
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75.50.Bb Fe and its alloys
75.60.Ch Domain walls and domain structure
81.30.Kf Martensitic transformations
64.70.K- Solid-solid transitions
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
61.05.jp Electron holography

Correlation between fractal dimension and reversal behavior of magnetic domain in Co/Pd nanomultilayers

Dong-Hyun Kim, Yoon-Chul Cho, Sug-Bong Choe, and Sung-Chul Shin

Appl. Phys. Lett. 82, 3698 (2003); http://dx.doi.org/10.1063/1.1578185 (3 pages) | Cited 6 times

Online Publication Date: 20 May 2003

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We report the experimental finding that there is a close correlation between fractal geometry and reversal mechanism of magnetic domain in Co/Pd nanomultilayers. We have measured the fractal dimension Df of magnetic domain as well as the wall-motion speed V, the nucleation rate R, and the reversal ratio V/R in Co/Pd nanomultilayer films during magnetization reversal via time-resolved direct domain observation. Interestingly enough, Df is inversely related to the reversal ratio V/R, which could be quantitatively explained using a micromagnetic simulation based on thermally activated relaxation model. We find that the fractal dimension is a crucial parameter to characterize magnetization reversal behavior as well as jaggedness of domain geometry. © 2003 American Institute of Physics.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.50.Cc Other ferromagnetic metals and alloys
75.60.Jk Magnetization reversal mechanisms
75.70.Kw Domain structure (including magnetic bubbles and vortices)
75.50.Tt Fine-particle systems; nanocrystalline materials

The energy barriers in antiferromagnetically coupled media

D. T. Margulies, A. Berger, A. Moser, M. E. Schabes, and Eric E. Fullerton

Appl. Phys. Lett. 82, 3701 (2003); http://dx.doi.org/10.1063/1.1578161 (3 pages) | Cited 12 times

Online Publication Date: 20 May 2003

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We study the physics of the energy barriers for magnetization reversal in antiferromagnetically coupled (AFC) media by means of temperature dependent magnetometry as well as modeling. We find that the energy barrier of the lower layer is fairly low, and mainly given by its anisotropy–volume product (KV). This means the lower layer magnetization is actually in thermal equilibrium, but the presence of the interlayer coupling makes the state with AF alignment of both layers thermodynamically so much more probable, that AFC media are thermally stable overall. The model further predicts that for typical values of the exchange coupling constant, the energy barrier of the composite system at zero field is essentially equal to the upper layer KV with the additional energy from the interlayer coupling being only a small perturbation. © 2003 American Institute of Physics.
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75.50.Ss Magnetic recording materials
75.60.Jk Magnetization reversal mechanisms
75.30.Gw Magnetic anisotropy
75.30.Et Exchange and superexchange interactions
75.50.Ee Antiferromagnetics

Fabrication of a vector Hall sensor for magnetic microscopy

D. Gregušová, V. Cambel, J. Fedor, R. Kúdela, J. Šoltýs, T. Lalinský, I. Kostič, and S. J. Bending

Appl. Phys. Lett. 82, 3704 (2003); http://dx.doi.org/10.1063/1.1577820 (3 pages) | Cited 9 times

Online Publication Date: 20 May 2003

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We have developed a micromachined Hall sensor for scanning the entire magnetic field vector whose active dimensions are an order of magnitude smaller (∼5 μm) than the smallest existing vector field sensor. It is realized by patterning three Hall probes on the tilted faces of epitaxy-overgrown GaAs-based pyramidal-shaped mesa structures. Data from these “tilted” Hall probes are used to reconstruct the full magnetic field vector. © 2003 American Institute of Physics.
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07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing

Magnetic properties and magneto-optical effect of Co0.5Fe2.5O4 nanostructured films

B. X. Gu

Appl. Phys. Lett. 82, 3707 (2003); http://dx.doi.org/10.1063/1.1573357 (3 pages) | Cited 8 times

Online Publication Date: 20 May 2003

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Co0.5Fe2.5O4 ferrite films with nanostructure have been prepared by rf sputtering on a quartz substrate and annealed at temperatures from 400 to 600 °C in air. The magnetic properties and magneto-optical effect have been studied. It has been found that nanocrystalline Co0.5Fe2.5O4 films exhibit good magnetic properties and a large magneto-optical effect. The magnetization, coercivity, remanence ratio, and maximum energy product are 455 emu/cm3, 2.8 kOe, 0.72 MGOe, and 2.4 MGOe, respectively. The magneto-optical Faraday rotation is <−3.4°/μm at short wavelength and 4°/μm at the wavelength of 740 nm. These characteristics make them very promising to be used for magneto-optical recording and for permanent magnets. The influence of the distribution of Co2+ ions on magnetic properties and magneto-optical effect has been discussed. © 2003 American Institute of Physics.
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75.50.Gg Ferrimagnetics
78.20.Ls Magneto-optical effects
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
75.50.Vv High coercivity materials
81.40.Rs Electrical and magnetic properties related to treatment conditions

Intrinsic and extrinsic properties of epitaxial Nd2Fe14B films

Ullrich Hannemann, Sebastian Fähler, Volker Neu, Bernhard Holzapfel, and Ludwig Schultz

Appl. Phys. Lett. 82, 3710 (2003); http://dx.doi.org/10.1063/1.1576913 (3 pages) | Cited 18 times

Online Publication Date: 20 May 2003

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Epitaxial Nd2Fe14B films with the c axis (easy magnetization axis) perpendicular to the film plane were prepared on a Ta(110) buffer on single crystalline Al2O3(0001) substrates using pulsed laser deposition. Due to the epitaxial film growth an almost perfect alignment of all magnetic moments perpendicular to the film plane is achieved. Coercivities up to 2 T are obtained for Nd-rich films where the Nd2Fe14B grains are magnetically decoupled. An analysis of the coercivity mechanism shows that the switching mechanism is nucleation dominated and the high coercivity is achieved by avoiding nucleation within the grains. Intrinsic properties like the spin reorientation temperature of 135 K and spin reorientation angle of 30° at 4.2 K of these films are in very good agreement to single crystal data. © 2003 American Institute of Physics.
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75.70.-i Magnetic properties of thin films, surfaces, and interfaces
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.30.Wx Spin crossover
75.30.Cr Saturation moments and magnetic susceptibilities

High magnetic field sensor using LaSb2

D. P. Young, R. G. Goodrich, J. F. DiTusa, S. Guo, P. W. Adams, Julia Y. Chan, and Donavan Hall

Appl. Phys. Lett. 82, 3713 (2003); http://dx.doi.org/10.1063/1.1577390 (3 pages) | Cited 14 times

Online Publication Date: 20 May 2003

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The magnetotransport properties of single crystals of the highly anisotropic layered metal LaSb2 are reported in magnetic fields up to 45 T with fields oriented both parallel and perpendicular to the layers. Below 10 K the perpendicular magnetoresistance of LaSb2 becomes temperature independent and is characterized by a 100-fold linear increase in resistance between 0 and 45 T with no evidence of quantum oscillations down to 50 mK. The Hall resistivity is hole-like and gives a high field carrier density of n ∼ 3×1020 cm−3. The feasibility of using LaSb2 for magnetic field sensors is discussed. © 2003 American Institute of Physics.
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75.47.Pq Other materials
07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
07.55.Ge Magnetometers for magnetic field measurements
75.47.De Giant magnetoresistance
72.20.My Galvanomagnetic and other magnetotransport effects
85.75.Nn Hybrid Hall devices
75.30.Gw Magnetic anisotropy

Shape effect on magnetization reversal in chains of interacting ferromagnetic elements

V. Novosad, M. Grimsditch, J. Darrouzet, J. Pearson, S. D. Bader, V. Metlushko, K. Guslienko, Y. Otani, H. Shima, and K. Fukamichi

Appl. Phys. Lett. 82, 3716 (2003); http://dx.doi.org/10.1063/1.1577808 (3 pages) | Cited 32 times

Online Publication Date: 20 May 2003

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The magnetization reversal in the chains of submicron square- and disk-shaped Permalloy dots with lateral size of 800 nm, thickness of 50 nm and variable inter dot distance was investigated by using the magneto-optical Kerr effect technique, magnetic force microscopy and micromagnetic modeling. We have found that the particle shape strongly affects the characteristic switching fields of well-separated dots, and has almost no influence on strength of inter dot interaction in chains of magnetostatically coupled elements. © 2003 American Institute of Physics.
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75.60.Jk Magnetization reversal mechanisms
75.50.Bb Fe and its alloys
75.75.-c Magnetic properties of nanostructures
75.50.Tt Fine-particle systems; nanocrystalline materials
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
78.20.Ls Magneto-optical effects
68.37.Rt Magnetic force microscopy (MFM)
75.30.Et Exchange and superexchange interactions

Optical detection of electron paramagnetic resonance in CdMnTe single quantum wells

M. L. Sadowski, M. Byszewski, M. Potemski, A. Sachrajda, and G. Karczewski

Appl. Phys. Lett. 82, 3719 (2003); http://dx.doi.org/10.1063/1.1578511 (3 pages) | Cited 5 times

Online Publication Date: 20 May 2003

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The electron paramagnetic resonance of Mn2+ ions localized in a CdTe quantum well is measured by an all-optical method. The photoluminescence transitions of a two-dimensional electron gas are used to monitor changes in the Mn spin polarization. The local character of this probe and the detection technique permit us to achieve a very high sensitivity for the number of spins detected (better than 108 spins). Two simultaneous effects are observed at resonance: A blueshift of the whole photoluminescence spectrum, and a dramatic transfer of photoluminescence intensity from neutral to negatively charged excitons. © 2003 American Institute of Physics.
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76.70.Hb Optically detected magnetic resonance (ODMR)
78.67.De Quantum wells
73.21.Fg Quantum wells
75.50.Pp Magnetic semiconductors
78.55.Hx Other solid inorganic materials
71.35.Pq Charged excitons (trions)

Approach to optimize the pinning effect of a NiMn layer with reduced thickness under a much shortened annealing process

B. Dai, J. W. Cai, W. Y. Lai, F. Shen, Z. Zhang, and G. H. Yu

Appl. Phys. Lett. 82, 3722 (2003); http://dx.doi.org/10.1063/1.1579118 (3 pages) | Cited 5 times

Online Publication Date: 20 May 2003

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We investigated the magnetic properties of sputtered Ni0.8Fe0.2/Ni1−xMnx (0.43 ⩽ x ⩽ 0.70) bilayers and found that an antiferromagnetic equiatomic NiMn layer could be formed through Mn diffusion with reduced thickness and a much shortened annealing time if the Ni1−xMnx layer is off-stoichiometric with suitable excess Mn. An overdose of Mn in a NiMn precursor layer was demonstrated to enhance the migration and the diffusion of Mn atoms, which seemed to promote the formation of antiferromagnetic NiMn of the θ phase, but in the mean time led to the deterioration of the adjacent ferromagnetic layer. We thus introduced the nano-oxide layer in the ferromagnetic layer near the interface of ferromagnetic and antiferromagnetic layers, which was proven to be very efficient to prevent Mn atoms from further intruding into the ferromagnetic layer even in the case that a large amount of Mn atoms were involved. As a result, a ferromagnetic layer pinned by a NiMn layer with excellent performance has been developed in a much simplified process. © 2003 American Institute of Physics.
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75.50.Ee Antiferromagnetics
75.70.Ak Magnetic properties of monolayers and thin films
75.30.Et Exchange and superexchange interactions
61.72.Cc Kinetics of defect formation and annealing

Dynamically tuning properties of epitaxial colossal magnetoresistance thin films

Darren Dale, Aaron Fleet, J. D. Brock, and Y. Suzuki

Appl. Phys. Lett. 82, 3725 (2003); http://dx.doi.org/10.1063/1.1578186 (3 pages) | Cited 34 times

Online Publication Date: 20 May 2003

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The strain state of epitaxial La0.5Sr0.5MnO3 thin films on BaTiO3 are dynamically tuned by temperature and substrate bias. The resistivity of the La0.5Sr0.5MnO3 thin films is particularly sensitive to changes in structure. Fractional changes in magnetization and resistivity as a function of temperature reveal a direct correlation with fractional changes in the structure, as measured by out-of-plane x-ray diffraction. Fractional changes in resistivity, as large as 30%, are observed for strain induced by the structural phase transitions of the BaTiO3 substrate, and a 12% change is induced by an inverse piezoelectric effect at room temperature. © 2003 American Institute of Physics.
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75.47.Lx Magnetic oxides
75.47.Gk Colossal magnetoresistance
75.50.Dd Nonmetallic ferromagnetic materials
75.70.Ak Magnetic properties of monolayers and thin films
68.60.Bs Mechanical and acoustical properties
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
68.55.-a Thin film structure and morphology
77.65.Ly Strain-induced piezoelectric fields

Detwinning YBa2Cu3O7−δ thin films

J. Nam, R. A. Hughes, A. Dabkowski, and J. S. Preston

Appl. Phys. Lett. 82, 3728 (2003); http://dx.doi.org/10.1063/1.1578166 (3 pages) | Cited 4 times

Online Publication Date: 20 May 2003

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Single crystals of YBa2Cu3O7-δ (YBCO) have been detwinned under the simultaneous application of heat and uniaxial stress. This approach, however, has proved futile in thin films as they become heavily twinned due to strain from the underlying substrate as well as the orthorhombic unit cell. This lack of control over twinning has made it difficult to determine the role that twins play in determining the transport properties of films. Here, we present a technique for detwinning YBCO thin films. The detwinning in YBCO thin film is achieved by suspending a portion of the YBCO film above the underlying substrate. The suspended material is no longer influenced by the confining effects of the substrate and this allows it to detwin under the application of a uniaxial stress brought about by an anneal. With this technique, we are able to produce high-quality detwinned regions that will help aid the understanding of transport mechanisms in YBCO. © 2003 American Institute of Physics.
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74.72.-h Cuprate superconductors
74.78.-w Superconducting films and low-dimensional structures
74.62.Bf Effects of material synthesis, crystal structure, and chemical composition
61.72.Mm Grain and twin boundaries

Uniaxial magnetic anisotropy and magnetic switching in La0.67Sr0.33MnO3 thin films grown on vicinal SrTiO3(100)

Zhi-Hong Wang, G. Cristiani, and H.-U. Habermeier

Appl. Phys. Lett. 82, 3731 (2003); http://dx.doi.org/10.1063/1.1578711 (3 pages) | Cited 31 times

Online Publication Date: 20 May 2003

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See Also: Publisher's Note

Show Abstract
La0.67Sr0.33MnO3 ultrathin films grown on vicinal SrTiO3(100) surface show an in-plane uniaxial magnetic anisotropy with easy axis along the substrate atomic steps generated by a 10° miscut off the (100) plane. Over a large angular range, the angular dependence of magnetic switching field is found to obey the 1/cos φ law, indicating that the magnetic reversal is completed by a 180° domain nucleation and sweeping along the easy axis. However, when the applied field is perpendicular to the hard axis (φ = 90°), the magnetization reversal is found to be well described by the Stoner–Wohlfarth model, in which the magnetization coherently rotates from the easy axis to hard axis. © 2003 American Institute of Physics.
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75.70.Ak Magnetic properties of monolayers and thin films
75.60.Jk Magnetization reversal mechanisms
75.30.Gw Magnetic anisotropy
75.50.Dd Nonmetallic ferromagnetic materials
75.47.Gk Colossal magnetoresistance
75.60.Ch Domain walls and domain structure
75.70.Kw Domain structure (including magnetic bubbles and vortices)
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