jap banner
  • Volume/Page
  • Keyword
  • DOI
  • Citation
  • Advanced
   
 
 
 

Flickr Twitter iResearch App Facebook

SECTION LISTING

BROWSE VOLUMES

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

15 May 2003

Volume 93, Issue 10, pp. 5855-8792

Return to All Sections
back to top
RSS Feeds

Phase transformation and magnetic moment in FePt nanoparticles

Y. Ding, S. Yamamuro, D. Farrell, and S. A. Majetich

J. Appl. Phys. 93, 7411 (2003); http://dx.doi.org/10.1063/1.1544495 (3 pages) | Cited 26 times

Online Publication Date: 9 May 2003

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The phase transformation from fcc to L10 in FePt nanoparticles was investigated in both thick film samples and self-assembled arrays as a function of the annealing temperature, using transmission electron microscopy, x-ray diffraction, differential scanning calorimetry, and magnetometry. A significant fraction of the surfactant decomposes into gaseous products below 500 °C, removing the steric barrier between particle cores. This causes the particles to coalesce at the same annealing temperatures where the transformation to the high anisotropy phase occurs. © 2003 American Institute of Physics.
Show PACS
75.50.Tt Fine-particle systems; nanocrystalline materials
61.46.-w Structure of nanoscale materials
75.30.Cr Saturation moments and magnetic susceptibilities
64.70.Nd Structural transitions in nanoscale materials
75.50.Bb Fe and its alloys

Effects of surface step and substrate temperature on nanostructure of L10–FePt nanoparticles

Kazuhisa Sato, Takenori Kajiwara, Masaru Fujiyoshi, Manabu Ishimaru, Yoshihiko Hirotsu, and Tadashi Shinohara

J. Appl. Phys. 93, 7414 (2003); http://dx.doi.org/10.1063/1.1541641 (3 pages) | Cited 6 times

Online Publication Date: 9 May 2003

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The variation of the particle size, particle density, and its relation to the hard magnetic properties of FePt nanoparticles with respect to substrate temperatures and substrate surface morphologies has been investigated. On geometrically flat surfaces, densely dispersed FePt nanoparticles with a particle density of 1012 cm−2 were obtained at a substrate temperature below 573 K, while substrate temperatures between 623 and 823 K are necessary for obtaining well-oriented and well-isolated L10–FePt nanoparticles with large coercivity. Isolated particles fabricated above 573 K did not coalesce largely upon annealing at 873 K, which can be attributed to the “anchoring effect” of Pt “seed” particles. The coercivity of FePt nanoparticles was measured at 300 K damped with decreasing particle sizes below 10 nm. High-density areal packing of Fe/Pt nanoparticles could be fabricated at 673 K on a slightly inclined NaCl(001) substrate with surface steps. These particles coalesced easily upon annealing along the 〈100〉 step edges. © 2003 American Institute of Physics.
Show PACS
75.50.Tt Fine-particle systems; nanocrystalline materials
61.46.-w Structure of nanoscale materials
75.50.Ss Magnetic recording materials
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
64.70.Nd Structural transitions in nanoscale materials
75.50.Vv High coercivity materials

Submicron Co(TaC) line array produced by electron-beam direct writing

Y. Zhao, T. J. Zhou, J. P. Wang, J. T. L. Thong, X. F. Yao, and T. C. Chong

J. Appl. Phys. 93, 7417 (2003); http://dx.doi.org/10.1063/1.1558254 (3 pages)

Online Publication Date: 9 May 2003

Full Text: Read Online (HTML) | Download PDF

Show Abstract
(Co60C40)97Ta3 and Co60C40 films with thickness 30 nm were prepared by cosputtering Co, Ta, and C onto C-buffered glass substrates. The as-deposited (Co60C40)97Ta3 and Co60C40 films were amorphous and nonferromagnetic. These films became magnetic upon annealing and the magnetic performance of annealed (Co60C40)97Ta3 films are better than that of annealed Co60C40 films at the same annealing condition. Magnetic patterning (line array) of the as-deposited (Co60C40)97Ta3 films was realized by subjecting it to electron-beam radiation using a focused 30 keV beam with a current of 7.1 nA and a dwell time per line of 0.75 s and longer. By increasing the dwell time, the whole region where an electron beam was scanned became magnetic with clear domain structures because of thermally activated diffusion. The required dwell time of magnetically patterning nonmagnetic (Co60C40)97Ta3 thin films (0.75 s) is much shorter than that of Co60C40 films (3.8 s). The magnetic measurements show that the lines [(Co60C40)97Ta3] and dots (Co60C40) are magnetically soft. The present method of magnetically patterning a nonmagnetic film has potential application for nanoscale solid magnetic devices. © 2003 American Institute of Physics.
Show PACS
81.16.Nd Micro- and nanolithography
75.70.Ak Magnetic properties of monolayers and thin films
61.80.Fe Electron and positron radiation effects
68.55.-a Thin film structure and morphology
61.72.Cc Kinetics of defect formation and annealing
81.40.Rs Electrical and magnetic properties related to treatment conditions
81.40.Gh Other heat and thermomechanical treatments
75.70.Kw Domain structure (including magnetic bubbles and vortices)
66.30.H- Self-diffusion and ionic conduction in nonmetals

Observation of ion beam induced magnetic patterning using off-specular polarized neutron reflectometry

N. D. Telling, S. Langridge, R. M. Dalgliesh, P. J. Grundy, and V. M. Vishnyakov

J. Appl. Phys. 93, 7420 (2003); http://dx.doi.org/10.1063/1.1544496 (3 pages) | Cited 5 times

Online Publication Date: 9 May 2003

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The long-range magnetic structure in Co/Pt multilayers magnetically patterned by ion irradiation is observed by off-specular polarized neutron reflectivity. While both specular and off-specular measurements indicate the formation of an artificial domain structure when the sample is in its remanent state, resonant peaks seen in the diffuse scatter reveal long-range magnetic ordering with periodicity in agreement with the design value. These peaks are completely suppressed when the sample is saturated in plane, confirming their origin in the magnetic patterning of the multilayer. © 2003 American Institute of Physics.
Show PACS
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.25.-j Spin arrangements in magnetically ordered materials (including neutron and spin-polarized electron studies, synchrotron-source x-ray scattering, etc.)
75.70.Kw Domain structure (including magnetic bubbles and vortices)
75.50.Cc Other ferromagnetic metals and alloys
61.80.Jh Ion radiation effects
61.82.Bg Metals and alloys
75.60.Ch Domain walls and domain structure
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

Magnetic properties of Sr-ferrite dot arrays by electron beam lithography

Xiaoxi Liu and Fumitake Itoh

J. Appl. Phys. 93, 7423 (2003); http://dx.doi.org/10.1063/1.1541642 (3 pages) | Cited 1 time

Online Publication Date: 9 May 2003

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We have successfully prepared Sr-ferrite dot arrays with perpendicular magnetic anisotropy by electron beam lithography. Virgin magnetic configurations detected by magnetic force microscopy (MFM) show single domain configuration for a 0.5 μm dot, while multidomain configurations are found for larger dots. The magnetization reversal mechanism in dots larger than 0.5 μm is found to be domain wall motion. While the magnetization reversal mechanism in 0.5 μm dots is found to be magnetization rotation. A normalized dc demagnetization remanence curve (DCD) measured by a superconducting quantum interference device (SQUID) indicates that with a decrease of dot size, the DCD curve is approaching the curve predicted by the coherent rotation model. Both MFM and SQUID results indicate that the single-domain dots reversed individually free from interdot magnetostatic coupling. © 2003 American Institute of Physics.
Show PACS
75.75.-c Magnetic properties of nanostructures
75.50.Gg Ferrimagnetics
75.60.Jk Magnetization reversal mechanisms
81.07.Ta Quantum dots
81.16.Nd Micro- and nanolithography
75.30.Gw Magnetic anisotropy
75.60.Ch Domain walls and domain structure
75.70.Kw Domain structure (including magnetic bubbles and vortices)
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
68.37.Rt Magnetic force microscopy (MFM)

Magnetization patterns of permalloy square frames

Mei-Feng Lai, Zung-Hang Wei, Ching-Ray Chang, J. C. Wu, W. Z. Hsieh, Nickolai A. Usov, Jun-Yang Lai, and Y. D. Yao

J. Appl. Phys. 93, 7426 (2003); http://dx.doi.org/10.1063/1.1558588 (3 pages) | Cited 3 times

Online Publication Date: 9 May 2003

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Four different magnetization configurations of micron- and submicron-sized permalloy square frames are investigated by numerical simulations and experiments. Beside the pure conventional 90° Neel type wall with zero net magnetic pole, we also obtain numerically another high energy domain wall with positive or negative net magnetic poles in the corner. These three kinds of domain walls constitute four different patterns in square frames. We compare the magnetic pole density distributions derived from the spin configurations of simulation results with the images taken by magnetic force microscopy, and find reasonable agreement between them. © 2003 American Institute of Physics.
Show PACS
75.60.Ch Domain walls and domain structure
75.70.Kw Domain structure (including magnetic bubbles and vortices)
75.50.Bb Fe and its alloys
68.37.Rt Magnetic force microscopy (MFM)
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.30.Et Exchange and superexchange interactions
75.30.Gw Magnetic anisotropy

Vortex pinning at individual defects in magnetic nanodisks

M. Rahm, J. Biberger, V. Umansky, and D. Weiss

J. Appl. Phys. 93, 7429 (2003); http://dx.doi.org/10.1063/1.1558255 (3 pages) | Cited 16 times

Online Publication Date: 9 May 2003

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We studied the interaction between magnetic vortices and artificial point defects by using micro-Hall magnetometry. Disk-shaped Permalloy particles with diameters between 300 and 800 nm and thicknesses from 20 to 60 nm, which contain a single lithographically defined defect, were examined. Magnetization reversal curves were measured for different in-plane directions of the applied field. The data indicate that the magnetic vortex structure can be pinned at the point defect. © 2003 American Institute of Physics.
Show PACS
75.60.Jk Magnetization reversal mechanisms
75.50.Tt Fine-particle systems; nanocrystalline materials
61.46.-w Structure of nanoscale materials
81.07.Wx Nanopowders
75.50.Bb Fe and its alloys
81.05.Bx Metals, semimetals, and alloys

Transition of magnetocrystalline anisotropy and domain structure in epitaxial Fe(001) nanomagnets

R. Pulwey, M. Zölfl, G. Bayreuther, and D. Weiss

J. Appl. Phys. 93, 7432 (2003); http://dx.doi.org/10.1063/1.1558256 (3 pages) | Cited 6 times

Online Publication Date: 9 May 2003

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The magnetocrystalline anisotropy of epitaxially grown bcc-Fe(001) films on GaAs(001) shows a transition from a fourfold intrinsic anisotropy in thick films to an uniaxial one in ultrathin films (<3 nm) and hence can be tuned by varying the film thickness. Here we investigate the consequence of such an anisotropy tuning for the magnetization configurations of nanomagnets. The thickness was varied between 2.5 and 30 nm in steps of 2.5 nm. Disks with diameters between 200 nm and 2 μm were patterned with electron beam lithography and ion beam etching. The remanent and ac-demagnetized states as well as the switching behavior were examined by magnetic force microscopy. In addition, we employed micromagnetic simulations to compare with the measured results. © 2003 American Institute of Physics.
Show PACS
75.70.Kw Domain structure (including magnetic bubbles and vortices)
75.50.Tt Fine-particle systems; nanocrystalline materials
75.30.Gw Magnetic anisotropy
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

Observation of a flux closure state in NiFe/IrMn exchange biased rings

Z. B. Guo, Y. K. Zheng, K. B. Li, Z. Y. Liu, P. Luo, Y. T. Shen, and Y. H. Wu

J. Appl. Phys. 93, 7435 (2003); http://dx.doi.org/10.1063/1.1544498 (3 pages) | Cited 12 times

Online Publication Date: 9 May 2003

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We have investigated the magnetic behaviors of the array of NiFe/IrMn rings, where a remarkably asymmetrical, kinked hysteresis loop has been observed in the sample. The kinked hysteresis loop has been attributed to the magnetization reversal, which starts from a single domain state to an opposite single domain state on one side of the loop, and takes place via the transition from a single domain state to a flux closure state and then into the opposite single domain state on the other side of the loop. This phenomenon is dramatically different from that of NiFe single layer rings. © 2003 American Institute of Physics.
Show PACS
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.75.-c Magnetic properties of nanostructures
75.30.Et Exchange and superexchange interactions
75.60.Jk Magnetization reversal mechanisms
75.50.Bb Fe and its alloys
75.50.Ee Antiferromagnetics
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.60.Ch Domain walls and domain structure
75.70.Kw Domain structure (including magnetic bubbles and vortices)
75.50.Tt Fine-particle systems; nanocrystalline materials

Modeling of hysteresis and magnetization curves for hexagonally ordered electrodeposited nanowires

P. S. Fodor, G. M. Tsoi, and L. E. Wenger

J. Appl. Phys. 93, 7438 (2003); http://dx.doi.org/10.1063/1.1541643 (3 pages) | Cited 11 times

Online Publication Date: 9 May 2003

Full Text: Read Online (HTML) | Download PDF

Show Abstract
A computational model has been developed to investigate how the magnetostatic interactions affect the hysteresis and magnetization curves for hexagonal arrays of magnetic nanowires. The magnetization coupling between nanowires arises from the stray fields produced by the other nanowires composing the array such that the field at each nanowire is the sum of the external field and the interaction field with the other nanowires. Using only two adjustable parameters: the interaction between nearest neighbors and the width of the Gaussian distribution in switching fields centered around the measured coercivity, simulations are compared with the experimentally measured hysteresis and magnetization curves for electrodeposited Co0.45Fe0.55 alloy nanowires with diameters from 12 to 48 nm. Excellent agreement is found for all nanowire systems except for the largest diameter arrays where deviations from the Gaussian distribution of switching fields need to be considered. © 2003 American Institute of Physics.
Show PACS
75.75.-c Magnetic properties of nanostructures
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.50.Bb Fe and its alloys
75.30.Gw Magnetic anisotropy

Magnetization reversal and domain structure of antiferromagnetically coupled submicron elements

N. Tezuka, N. Koike, K. Inomata, and S. Sugimoto

J. Appl. Phys. 93, 7441 (2003); http://dx.doi.org/10.1063/1.1539074 (3 pages) | Cited 20 times

Online Publication Date: 9 May 2003

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Switching characteristics and magnetic domain structures in submicron size synthetic antiferromagnets (SyAF), Co90Fe10/Ru/Co90Fe10 have been studied. Submicron size elements with well defined geometry were prepared by electron beam lithography and argon ion milling for SyAFs and Co90Fe10 monolayers deposited by an ultrahigh vacuum sputtering system. Hysteresis loops were obtained by a focused magneto-optic Kerr effect (MOKE) system and magnetic images in the remanent state were observed by magnetic force microscopy (MFM). We found that the MFM images of SyAF exhibit a single domain structure even in the case of aspect ratio of 1, and there is an optimum ferromagnetic film thickness at which SyAF can obtain a single domain structure with such a low aspect ratio. The MOKE results show that the switching field is dependent on the element width and aspect ratio. © 2003 American Institute of Physics.
Show PACS
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.60.Jk Magnetization reversal mechanisms
75.70.Kw Domain structure (including magnetic bubbles and vortices)
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.50.Ee Antiferromagnetics
75.50.Bb Fe and its alloys
78.20.Ls Magneto-optical effects
75.60.Ch Domain walls and domain structure
75.30.Et Exchange and superexchange interactions

Domain-wall trapping in a ferromagnetic nanowire network

E. Saitoh, M. Tanaka, H. Miyajima, and T. Yamaoka

J. Appl. Phys. 93, 7444 (2003); http://dx.doi.org/10.1063/1.1544499 (3 pages) | Cited 8 times

Online Publication Date: 9 May 2003

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The magnetic domain configuration in a submicron Ni81Fe19 wire network has been investigated by magnetic force microscopy. To improve the responsivity of the magnetic force microscope, an active quality factor autocontrol method was adopted. In the remanent state, domain walls were observed trapped firmly at the vertexes of the network. The magnetic domain configurations appear to minimize the exchange energy at the vertexes. These results indicate that the magnetic property of the ferromagnetic network can be described in terms of the uniform magnetic moments of the wires and interwire magnetic interactions at the vertexes. The observed structure of the domain walls is well reproduced by micromagnetic simulations. © 2003 American Institute of Physics.
Show PACS
75.75.-c Magnetic properties of nanostructures
75.70.Kw Domain structure (including magnetic bubbles and vortices)
75.60.Ch Domain walls and domain structure
75.50.Bb Fe and its alloys
68.37.Rt Magnetic force microscopy (MFM)
75.30.Et Exchange and superexchange interactions
75.30.Cr Saturation moments and magnetic susceptibilities
Return to All Sections
Close

Google Calendar

ADVERTISEMENT

Go to AIP Home   © AIP Publishing LLC
close