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

16 Nov 1998

Volume 73, Issue 20, pp. 2857-3009

Return to All Sections
back to top
RSS Feeds

Doping effects arising from Fe and Ge for Mn in La0.7Ca0.3MnO3

J. R. Sun, G. H. Rao, B. G. Shen, and H. K. Wong

Appl. Phys. Lett. 73, 2998 (1998); http://dx.doi.org/10.1063/1.122656 (3 pages) | Cited 47 times

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Structural, magnetic, and transport properties of polycrystalline La0.7Ca0.3Mn1−xFexO3 and La0.7Ca0.3Mn1−xGexO3 are experimentally studied. Single-phase samples are obtained in the range x = 0–0.12 for Fe, and x = 0–0.06 for Ge. There are no appreciable structure changes due to the introduction of Fe and Ge. The Mn-site doping favors a reduced magnetic/resistive transition, at rates of ∼22 K for 1% Fe and ∼28 K for 1% Ge, and an elevated resistivity. No metal–insulator transition occurs when the content of Fe exceeds ∼0.1. The enhanced doping effects in La0.7Ca0.3Mn1−xGexO3 can be ascribed to the reduced hole concentration noting that the presence of Fe and Ge influence the contents of mobile eg electrons and holes in the compounds, respectively. Equivalence of the effects from Fe and Ge doping, respectively, to those due to eg electron and hole trapping and the relation between Mn- and O-site doping are discussed. © 1998 American Institute of Physics.
Show PACS
72.60.+g Mixed conductivity and conductivity transitions
61.72.up Other materials
75.50.Dd Nonmetallic ferromagnetic materials
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
72.20.Fr Low-field transport and mobility; piezoresistance
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
72.80.Sk Insulators
61.66.Fn Inorganic compounds

Hydrogenation disproportionation desorption recombination in Sm–Co alloys by means of reactive milling

O. Gutfleisch, M. Kubis, A. Handstein, K.-H. Müller, and L. Schultz

Appl. Phys. Lett. 73, 3001 (1998); http://dx.doi.org/10.1063/1.122657 (3 pages) | Cited 18 times

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Sm–Co-type alloys were disproportionated by milling in hydrogen at enhanced temperatures. X-ray diffraction confirmed the disproportionation of the SmCo5 and Sm2Co17 phases into Sm hydride and α-Co. This “reactive milling” procedure facilitates the disproportionation of these alloys which are characterized by a very high thermodynamic stability, and therefore are not available for a standard hydrogenation disproportionation desorption recombination treatment. Recombination of the reactively milled powders leads to the formation of the original phases, now with dramatically refined grain sizes of around 25 nm and significant coercivities such as μ0JHC = 3.7 T in the case of the SmCo5 alloy. Exchange coupling between the nanoscaled grains resulted in magnetically single phase behavior despite a multiphase microstructure. In particular, for the Sm2Co17 alloy, a remanence enhancement was observed for recombination temperatures ⩽ 700 °C. © 1998 American Institute of Physics.
Show PACS
75.50.Ww Permanent magnets
81.05.Bx Metals, semimetals, and alloys
81.20.Wk Machining, milling
75.50.Kj Amorphous and quasicrystalline magnetic materials
81.20.Ev Powder processing: powder metallurgy, compaction, sintering, mechanical alloying, and granulation
75.50.Cc Other ferromagnetic metals and alloys
75.50.Tt Fine-particle systems; nanocrystalline materials
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
81.07.-b Nanoscale materials and structures: fabrication and characterization

Fabrication and physical properties of c-axis oriented thin films of layered perovskite La2−2xSr1+2xMn2O7

Y. Konishi, T. Kimura, M. Izumi, M. Kawasaki, and Y. Tokura

Appl. Phys. Lett. 73, 3004 (1998); http://dx.doi.org/10.1063/1.122658 (3 pages) | Cited 24 times

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We have grown c-axis oriented films of a layered perovskite La2−2xSr1+2xMn2O7 (x = 0.4) by pulsed laser deposition under the limited growth condition; above 900 °C and below 100 mTorr for substrate temperature and oxygen pressure (PO2), respectively. Otherwise, epitaxial but composition-unidentified films were deposited. The films show a resistive transition around 100 K in coincidence with the magnetic transition. The value of resistivity at low temperature is larger than that of a single crystal by about two orders of magnitude, perhaps due to the canted spin ordering. The films show gigantic magnetoresistance accompanied with hysteresis. © 1998 American Institute of Physics.
Show PACS
75.70.Ak Magnetic properties of monolayers and thin films
75.47.De Giant magnetoresistance
81.15.Fg Pulsed laser ablation deposition
81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)
72.60.+g Mixed conductivity and conductivity transitions
81.15.Kk Vapor phase epitaxy; growth from vapor phase
75.50.Cc Other ferromagnetic metals and alloys
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
75.25.-j Spin arrangements in magnetically ordered materials (including neutron and spin-polarized electron studies, synchrotron-source x-ray scattering, etc.)
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

Abnormal temperature dependence of intrinsic coercivity in Sm(Co, Fe, Cu, Zr)z powder materials

J. F. Liu, T. Chui, D. Dimitrov, and G. C. Hadjipanayis

Appl. Phys. Lett. 73, 3007 (1998); http://dx.doi.org/10.1063/1.122659 (3 pages) | Cited 57 times

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The intrinsic coercivity Hci in Sm(CobalCuxFe0.1Zr0.033)z powder materials was found to increase with increasing temperature when Cu content x = 0.048, but to decrease when Cu content x ≥ 0.068. This abnormal behavior, which is also reversible, was found in a series of samples with various ratios z. The field dependence of the intrinsic coercivity suggests that the bonded magnets were fully saturated with an applied field of 20 kOe. The exposure to higher temperatures did not change the room temperature value of coercivity. This indicates that the microstructure does not change during the measurement from 573 to 773 K. The change of coercivity mechanism was found to be responsible for this abnormal temperature behavior. Monte Carlo simulation showed that the coercivity increases (decreases) with increasing temperature for the repulsive (attractive) cell boundary, which is consistent with the experimental results. © 1998 American Institute of Physics.
Show PACS
75.50.Ww Permanent magnets
75.50.Vv High coercivity materials
75.50.Tt Fine-particle systems; nanocrystalline materials
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.50.Bb Fe and its alloys
75.50.Cc Other ferromagnetic metals and alloys
Return to All Sections
Close

Google Calendar

ADVERTISEMENT

Go to AIP Home   © AIP Publishing LLC
close