APL Nameplate
  • Volume/Page
  • Keyword
  • DOI
  • Citation
  • Advanced
   
 
 
 

Flickr Twitter iResearch App Facebook

BROWSE VOLUMES

Year Range: 
Search Issue | RSS Feeds RSS
Previous Issue Next Issue

26 Mar 2007

Volume 90, Issue 13, Articles (13xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 90, 134101 (2007); http://dx.doi.org/10.1063/1.2679209 (3 pages)

S. Srinivasan, J. Hiller, B. Kabius, and O. Auciello
Enlarge Image | Read More
Return to All Sections
back to top
RSS Feeds

Vortex motion in chilarity-controlled pair of magnetic disks

T. Kimura, Y. Otani, H. Masaki, T. Ishida, R. Antos, and J. Shibata

Appl. Phys. Lett. 90, 132501 (2007); http://dx.doi.org/10.1063/1.2716861 (3 pages) | Cited 25 times

Online Publication Date: 26 March 2007

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The authors investigate the influence of the vortex chirality on the magnetization processes of a magnetostatically coupled pair of magnetic disks. The magnetic vortices with opposite chiralities are realized by introducing asymmetry into the disks. The motion of the paired vortices are studied by measuring the magnetoresistance with a lock-in resistance bridge technique. The vortex annihilation process is found to depend on the moving directions of the magnetic vortices. The experimental results are well reproduced by the micromagnetic simulation.
Show PACS
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.47.Np Metals and alloys
75.40.Mg Numerical simulation studies
72.15.Gd Galvanomagnetic and other magnetotransport effects

Detection of weak ( ∼ 0.5–300 nT), low frequency (5–100 Hz) magnetic fields at room temperature by kilohertz modulation of the magneto-optical hysteresis in rare earth–iron garnet films

J. M. Hafez, J. Gao, and J. G. Eden

Appl. Phys. Lett. 90, 132502 (2007); http://dx.doi.org/10.1063/1.2713144 (3 pages) | Cited 1 time

Online Publication Date: 27 March 2007

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Periodic magnetic fields with frequencies in the 5–100 Hz range and peak strengths as low as 0.5 nT have been detected at 300 K by modulating at kHz rates the magneto-optical response of epitaxial (Tm,Bi)3(Ga,Fe)5O12 rare earth–iron garnet films at λ = 532 nm. By exploiting the ∼ 1°/μT slope of the magneto-optical transition region between the two magnetization states of these low coercivity (<0.5 mT) films, sub-nT field strengths can be measured by upconverting the detection process into the kHz domain. The domain wall velocities are measured to be 3–30 m/s for modulation frequencies in the 0.3–10 kHz interval, and the noise generated by wall motion appears to be the primary barrier to further reductions in the detection sensitivity floor. Films with thicknesses of 2–4 μm and mean domain widths of 3–6 mm exhibit figures of merit (Θ/α) of ∼ 3°–8.5° at 532 nm. Imaging of mesoscopic magnetic particles is demonstrated with a spatial resolution of <300 μm.
Show PACS
75.70.Ak Magnetic properties of monolayers and thin films
78.66.Nk Insulators
68.55.-a Thin film structure and morphology
75.60.Ch Domain walls and domain structure
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
78.20.Ls Magneto-optical effects

X-ray photoemission study of CoFeB/MgO thin film bilayers

J. C. Read, P. G. Mather, and R. A. Buhrman

Appl. Phys. Lett. 90, 132503 (2007); http://dx.doi.org/10.1063/1.2717091 (3 pages) | Cited 30 times

Online Publication Date: 27 March 2007

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The authors present results from an x-ray photoemission spectroscopy study of CoFeB/MgO bilayers where they observe process-dependent formation of B, Fe, and Co oxides at the CoFeB/MgO interface due to oxidation of CoFeB during MgO deposition. Vacuum annealing reduces the Co and Fe oxides but further incorporates B into the MgO forming a composite MgBxOy layer. Inserting an Mg layer between CoFeB and MgO introduces an oxygen sink, providing increased control over B content in the barrier.
Show PACS
79.60.Jv Interfaces; heterostructures; nanostructures
61.72.Cc Kinetics of defect formation and annealing
68.65.Ac Multilayers

Saturation and intrinsic dynamics of fluxons in NbTi and MgB2

R. V. Chamberlin, N. Newman, R. Gandikota, R. K. Singh, and B. H. Moeckly

Appl. Phys. Lett. 90, 132504 (2007); http://dx.doi.org/10.1063/1.2717111 (3 pages) | Cited 1 time

Online Publication Date: 27 March 2007

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The authors measured the remanent magnetization of superconducting NbTi and MgB2 as a function of time after removing an applied field. At similar reduced temperatures, the density of magnetic flux quanta (fluxons) is found to relax faster in NbTi than in MgB2. Nearer the transition, the relaxation rate in both materials exhibits a saturation that is independent of the initially applied field. This saturation occurs when the distance between fluxons is comparable to the London penetration depth. The temperature dependence of the saturation and time dependence of the relaxation can be characterized by the Anderson-Kim model [Rev. Mod. Phys. 36, 39 (1964) ] for fluxon dynamics.
Show PACS
74.70.Ad Metals; alloys and binary compounds (including A15, MgB2, etc.)
74.25.Uv Vortex phases (includes vortex lattices, vortex liquids, and vortex glasses)
74.25.Ha Magnetic properties including vortex structures and related phenomena

Synthetic antiferromagnet for hard layer of exchange coupled composite media

Stephanie Hernandez, Manish Kapoor, and R. H Victora

Appl. Phys. Lett. 90, 132505 (2007); http://dx.doi.org/10.1063/1.2716860 (3 pages) | Cited 7 times

Online Publication Date: 28 March 2007

Full Text: Read Online (HTML) | Download PDF

Show Abstract
It has been shown that exchange coupled composite (ECC) media exhibit a superior thermal stability to switching field ratio compared to conventional perpendicular media. However, optimal media designs have employed a low magnetization hard layer. A more physically achievable design may consist of replacing the hard layer with a synthetic antiferromagnet consisting of two ferromagnetic hard layers coupled by an antiferromagnetic exchange interaction. This approach is shown to decrease the switching field and increases the thermal stability ratio when compared to ECC media with a single hard layer.
Show PACS
75.30.Et Exchange and superexchange interactions
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.50.Ee Antiferromagnetics
75.50.Ss Magnetic recording materials

Spin torque and heating effects in current-induced domain wall motion probed by transmission electron microscopy

F. Junginger, M. Kläui, D. Backes, U. Rüdiger, T. Kasama, R. E. Dunin-Borkowski, L. J. Heyderman, C. A. F. Vaz, and J. A. C. Bland

Appl. Phys. Lett. 90, 132506 (2007); http://dx.doi.org/10.1063/1.2709989 (3 pages) | Cited 26 times

Online Publication Date: 28 March 2007

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Observations of domain wall motion and transformations due to injected current pulses in permalloy zigzag structures using off-axis electron holography and Lorentz microscopy are reported. Heating on membranes leads to thermally activated random behavior at low current densities and by backcoating the SiN membranes with Al, heating effects are significantly reduced. A set of indicators is devised to separate unambiguously spin torque effects from heating and it is shown that by using the Al layer the structures are sufficiently cooled to exhibit current-induced domain wall motion due to spin torque.
Show PACS
75.60.Ch Domain walls and domain structure
81.40.Gh Other heat and thermomechanical treatments

Perpendicular magnetization of L10-ordered FePt films in the thinnest limit

S. Imada, A. Yamasaki, S. Suga, T. Shima, and K. Takanashi

Appl. Phys. Lett. 90, 132507 (2007); http://dx.doi.org/10.1063/1.2717516 (3 pages) | Cited 17 times

Online Publication Date: 28 March 2007

Full Text: Read Online (HTML) | Download PDF

Show Abstract
L10-ordered FePt ultrathin films with thickness down to subnanometer range were fabricated by alternate monatomic layer (ML) deposition of Fe and Pt on Pt (001) substrate and were capped by Pt. Perpendicular Fe magnetic moment under magnetic field, together with that under remanence, was detected by soft x-ray magnetic circular dichroism. Pt/(Fe 1 ML/Pt 1 ML)3/Pt (001), whose FePt layer is ∼ 1 nm thick, showed perpendicular remanent magnetization at room temperature. At low temperatures, perpendicular remanent magnetization was found even at the thinnest end, i.e., 1 ML Fe sandwiched by Pt (001).
Show PACS
75.70.Ak Magnetic properties of monolayers and thin films
75.30.Cr Saturation moments and magnetic susceptibilities
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.50.Bb Fe and its alloys
78.20.Ls Magneto-optical effects
78.70.Dm X-ray absorption spectra

Spin transfer switching in dual MgO magnetic tunnel junctions

Zhitao Diao, Alex Panchula, Yunfei Ding, Mahendra Pakala, Shengyuan Wang, Zhanjie Li, Dmytro Apalkov, Hideyasu Nagai, Alexander Driskill-Smith, Lien-Chang Wang, Eugene Chen, and Yiming Huai

Appl. Phys. Lett. 90, 132508 (2007); http://dx.doi.org/10.1063/1.2717556 (3 pages) | Cited 31 times

Online Publication Date: 28 March 2007

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Dual magnetic tunnel junction (MTJ) structures consisting of two MgO insulating barriers of different resistances, two pinned reference layers aligned antiparallel to one another, and a free layer embedded between the two insulating barriers have been developed. The electron transport and spin dependent resistances in the dual MTJ structures are accounted for by sequential tunneling with some spin-flip relaxation in the central electrode (the free layer). With a tunneling magnetoresistance ratio of 70%, a switching current density Jc (at 30 ms) of 0.52 MA/cm2 is obtained, corresponding to an intrinsic value of Jc0 (at 1 ns) of 1.0 MA/cm2. This value of Jc0 is 2–3 times smaller than that of a single MgO insulating barrier MTJ structure and results from improvements in the spin-transfer torque efficiency. The asymmetry between JcAP→P and JcP→AP is significantly improved, which widens the read-write margin for memory device design. In addition, the experimental results show that the switching current density can be further reduced when an external field is applied along the hard axis of the free layer.
Show PACS
85.75.Dd Magnetic memory using magnetic tunnel junctions
72.20.My Galvanomagnetic and other magnetotransport effects
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

On the latent heat of high-temperature spin reorientation transitions

Michael D. Kuz’min and Manuel Richter

Appl. Phys. Lett. 90, 132509 (2007); http://dx.doi.org/10.1063/1.2718271 (2 pages) | Cited 6 times

Online Publication Date: 28 March 2007

Full Text: Read Online (HTML) | Download PDF

Show Abstract
If a 3d-4f magnet experiences a spin reorientation at a high temperature, it proceeds in an abrupt fashion, as a first-order phase transition, and is accompanied by release or absorption of heat. It is demonstrated that this latent heat amounts to two times the anisotropy constant of the 3d sublattice. This prediction is corroborated by the available experimental data. The same approach provides an estimate for the accompanying entropy change, which suggests that spin reorientation transitions cannot compete in this respect with ferromagnetism-paramagnetism or ferro-magnetism-antiferromagnetism transitions.
Show PACS
75.40.Gb Dynamic properties (dynamic susceptibility, spin waves, spin diffusion, dynamic scaling, etc.)
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.30.Gw Magnetic anisotropy
65.40.G- Other thermodynamical quantities

On the formation of voids in internal tin Nb3Sn superconductors

C. Scheuerlein, M. Di Michiel, and A. Haibel

Appl. Phys. Lett. 90, 132510 (2007); http://dx.doi.org/10.1063/1.2716346 (3 pages) | Cited 14 times

Online Publication Date: 29 March 2007

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The formation of voids during the reaction heat treatment of internal tin Nb3Sn strands degrades the physical superconductor properties. The authors describe three void growth mechanisms on the basis of combined synchrotron microtomography and x-ray diffraction results obtained during in situ heating cycles. Initially, void growth is driven by a reduction of void surface area. The main void volume increase is caused by density changes during the formation of Cu3Sn in the strand. Long duration temperature ramps and isothermal holding steps neither reduce the void volume nor improve the chemical strand homogeneity prior to the superconducting A15 phase nucleation and growth.
Show PACS
74.70.Ad Metals; alloys and binary compounds (including A15, MgB2, etc.)
61.72.Qq Microscopic defects (voids, inclusions, etc.)
81.40.Gh Other heat and thermomechanical treatments

Magnetic properties of Ni-doped MgO diluted magnetic insulators

S. Ramachandran, J. Narayan, and J. T. Prater

Appl. Phys. Lett. 90, 132511 (2007); http://dx.doi.org/10.1063/1.2717574 (3 pages) | Cited 8 times

Online Publication Date: 29 March 2007

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Magnesium oxide doped with Ni has been studied in two different forms: one in which the Ni ions are incorporated into the substitutional sites and the other in which Ni is present both in substitutional sites and in the form of metallic Ni precipitates embedded in the MgO matrix. Magnetic properties of these materials have been studied and correlated with the microstructural properties. There is a significant difference in the magnetic properties between the two forms. From these studies the authors envisage that a diluted magnetic insulator will be paramagnetic in the absence of intrinsic defects such as vacancies and interstitials. MgO is a good system to perform the present studies as it can be synthesized as a high quality crystal devoid of defects to a high degree. Moreover, the magnetic properties of the Ni precipitates can be used to compare the results when a diluted magnetic semiconductor material is not fully devoid of nanoclusters/precipitates and secondary phases.
Show PACS
75.20.Ck Nonmetals
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

Structural and magnetic properties of epitaxially grown Ge1−xFex thin films: Fe concentration dependence

Yusuke Shuto, Masaaki Tanaka, and Satoshi Sugahara

Appl. Phys. Lett. 90, 132512 (2007); http://dx.doi.org/10.1063/1.2718270 (3 pages) | Cited 7 times

Online Publication Date: 29 March 2007

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Ge1−xFex films (x = 2.0%–24.0%) grown by low-temperature molecular beam epitaxy were shown to have a diamond-type crystal structure without any other crystallographic phase of precipitates, although they contain slightly nonuniform Fe distribution and tiny stacking fault defects. The lattice constant decreases linearly with increasing the Fe content x from 0% to 13.0%, and is saturated for x>13.0%. The Curie temperature (TC) increases in proportion to x ( ⩽ 13.0%) and is saturated for x>13.0%. The maximum TC value was ∼ 170 K at x>13.0%. The structural and magnetic properties indicate that Ge1−xFex is an “intrinsic” ferromagnetic semiconductor.
Show PACS
68.55.-a Thin film structure and morphology
75.70.Ak Magnetic properties of monolayers and thin films
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
75.50.Pp Magnetic semiconductors

I‐V characteristics of La1.84Sr0.16CuO4/Nb-doped SrTiO3 heterojunction

X. Q. Xiang, J. F. Qu, Y. Q. Zhang, X. L. Lu, T. F. Zhou, G. Li, and X. G. Li

Appl. Phys. Lett. 90, 132513 (2007); http://dx.doi.org/10.1063/1.2719154 (3 pages) | Cited 6 times

Online Publication Date: 30 March 2007

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Current-voltage (I‐V) characteristics of the La1.84Sr0.16CuO4/1.0 wt % Nb-doped SrTiO3 heterojunction were measured in the temperature range from 5 to 290 K under magnetic fields up to 14 T. All I‐V curves show a fine rectifying property. A visible reduction of the diffusion potential (Vd) can be observed at the superconducting transition temperature due to the opening of the superconducting gap in La1.84Sr0.16CuO4. The reduction of Vd from its original track, ΔVd, is found to be of similar temperature and field dependencies as those of the superconducting gap. This suggests an alternative technique for detecting the superconductivity related features in superconducting films.
Show PACS
74.78.-w Superconducting films and low-dimensional structures
74.72.-h Cuprate superconductors
74.25.Jb Electronic structure (photoemission, etc.)
74.25.F- Transport properties
Return to All Sections
Close

Google Calendar

ADVERTISEMENT

Go to AIP Home   © AIP Publishing LLC
close