Large Magnetoresistance at Room Temperature in Organic Semiconductor Sandwich Devices

2005 ◽  
Vol 871 ◽  
Author(s):  
Govindarajan Veeraraghavan ◽  
Omer Mermer ◽  
Thomas Lee Francis ◽  
Yugang Sheng ◽  
Tho Duc Nguyen ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Film Thickness ◽  
Organic Semiconductors ◽  
Applied Magnetic Field ◽  
Room Temperature ◽  
Electrode Materials ◽  
Bulk Material ◽  
Temperature Dependent ◽  
Semiconducting Polymer ◽  
Mr Effect

AbstractWe describe a recently discovered magnetoresistance (MR) effect in semiconducting polymer and small molecule sandwich devices. The MR effect reaches up to 10% in a magnetic field of 10mT at room temperature. This MR effect is therefore amongst the largest of any bulk material. We characterize this effect and discuss its dependence on voltage, film thickness, temperature, electrode materials and (unintentional) impurity concentration in three different organic semiconductors. We found that the MR effect is only weakly temperature dependent and does not depend on sign and direction of the applied magnetic field. To the best of our knowledge, the discovered MR effect is not adequately described by any of the mechanisms known to date.

Magnetic Field Sensors based on Magnetoresistance Effect in Organic Semiconductor Sandwich Devices

2005 ◽  
Vol 906 ◽  
Author(s):  
Govindarajan Veeraraghavan ◽  
Ömer Mermer ◽  
Yugang Sheng ◽  
Tho Duc Nguyen ◽  
Thomas Lee Francis ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Organic Semiconductor ◽  
Room Temperature ◽  
Experimental Characterization ◽  
Magnetoresistance Effect ◽  
Temperature Dependent ◽  
Magnetic Field Sensors ◽  
Mr Effect ◽  
Alternating Magnetic Fields

AbstractWe describe magnetic field sensors based on a recently discovered magnetoresistance (MR) effect in nonmagnetic organic semiconductor sandwich devices. The MR effect reaches up to 10% in a magnetic field of 10 mT at room temperature. We perform an extensive experimental characterization of this effect. We found that the MR effect is only weakly temperature dependent and does not depend on sign and direction of the applied magnetic field. We also measured the device response to alternating magnetic fields up to 100 kHz. To the best of our knowledge, the discovered MR effect is not adequately described by any of the MR mechanisms known to date.

(111) Monocrystalline Nickel Films

1972 ◽  
Vol 30 ◽  
pp. 512-513
Author(s):  
T.E. Pratt ◽  
R.W. Vook
Keyword(s):  
Film Thickness ◽  
Deposition Rate ◽  
Room Temperature ◽  
Narrow Range ◽  
High Vacuum ◽  
Residual Pressure ◽  
Temperature Dependent ◽  
Deposition Parameters ◽  
Transmission Electron ◽  
Substrate Temperatures

(111) oriented thin monocrystalline Ni films have been prepared by vacuum evaporation and examined by transmission electron microscopy and electron diffraction. In high vacuum, at room temperature, a layer of NaCl was first evaporated onto a freshly air-cleaved muscovite substrate clamped to a copper block with attached heater and thermocouple. Then, at various substrate temperatures, with other parameters held within a narrow range, Ni was evaporated from a tungsten filament. It had been shown previously that similar procedures would yield monocrystalline films of CU, Ag, and Au.For the films examined with respect to temperature dependent effects, typical deposition parameters were: Ni film thickness, 500-800 A; Ni deposition rate, 10 A/sec.; residual pressure, 10-6 torr; NaCl film thickness, 250 A; and NaCl deposition rate, 10 A/sec. Some additional evaporations involved higher deposition rates and lower film thicknesses.Monocrystalline films were obtained with substrate temperatures above 500° C. Below 450° C, the films were polycrystalline with a strong (111) preferred orientation.

scholarly journals Semiconducting polymer blends that exhibit stable charge transport at high temperatures

Science ◽  
2018 ◽  
Vol 362 (6419) ◽  
pp. 1131-1134 ◽  
Author(s):  
Aristide Gumyusenge ◽  
Dung T. Tran ◽  
Xuyi Luo ◽  
Gregory M. Pitch ◽  
Yan Zhao ◽  
...  
Keyword(s):  
High Temperature ◽  
Polymer Blends ◽  
Charge Transport ◽  
Organic Semiconductors ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Hole Mobility ◽  
General Strategy ◽  
Semiconducting Polymer ◽  
High Temperature Operation

Although high-temperature operation (i.e., beyond 150°C) is of great interest for many electronics applications, achieving stable carrier mobilities for organic semiconductors at elevated temperatures is fundamentally challenging. We report a general strategy to make thermally stable high-temperature semiconducting polymer blends, composed of interpenetrating semicrystalline conjugated polymers and high glass-transition temperature insulating matrices. When properly engineered, such polymer blends display a temperature-insensitive charge transport behavior with hole mobility exceeding 2.0 cm2/V·s across a wide temperature range from room temperature up to 220°C in thin-film transistors.

scholarly journals Colossal Negative Magnetoresistance Effect in a La1.37Sr1.63Mn2O7 Single Crystal Grown by Laser-Diode-Heated Floating-Zone Technique

Crystals ◽  
2020 ◽  
Vol 10 (6) ◽  
pp. 547
Author(s):  
Si Wu ◽  
Yinghao Zhu ◽  
Junchao Xia ◽  
Pengfei Zhou ◽  
Haiyong Ni ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Single Crystal ◽  
Laser Diode ◽  
Room Temperature ◽  
Floating Zone ◽  
Magnetoresistance Effect ◽  
X Ray ◽  
Mr Effect ◽  
Distinct Features ◽  
The Magnetic Field

We have grown La 1.37 Sr 1.63 Mn 2 O 7 single crystals with a laser-diode-heated floating-zone furnace and studied the crystallinity, structure, and magnetoresistance (MR) effect by in-house X-ray Laue diffraction, X-ray powder diffraction, and resistance measurements. The La 1.37 Sr 1.63 Mn 2 O 7 single crystal crystallizes into a tetragonal structure with space group I4/mmm at room temperature. At 0 T, the maximum resistance centers around ∼166.9 K. Below ∼35.8 K, it displays an insulating character with an increase in resistance upon cooling. An applied magnetic field of B = 7 T strongly suppresses the resistance indicative of a negative MR effect. The minimum MR value equals −91.23% at 7 T and 128.7 K. The magnetic-field-dependent resistance shows distinct features at 1.67, 140, and 322 K, from which we calculated the corresponding MR values. At 14 T and 140 K, the colossal negative MR value is down to −94.04(5)%. We schematically fit the MR values with different models for an ideal describing of the interesting features of the MR value versus B curves.

Experimental Tests of Possible Mechanisms for the Organic Magnetoresistive Effect

2007 ◽  
Vol 1032 ◽  
Author(s):  
Tho Duc Nguyen ◽  
James Rybicki ◽  
Yugang Sheng ◽  
Markus Wohlgenannt
Keyword(s):  
Magnetic Field ◽  
Organic Semiconductors ◽  
Electrode Materials ◽  
Spin Dynamics ◽  
Experimental Tests ◽  
Triplet Exciton ◽  
Side Chain ◽  
Singlet Exciton ◽  
Organic Magnetoresistance ◽  
Magnetoresistive Effect

AbstractWe experimentally test three existing models of organic magnetoresistance (OMAR) which are all based on carrier spin dynamics. We first prove that hyperfine field originating from the hydrogen nuclei in organic materials is necessary for observing OMAR by studying C60 sandwich devices using several different electrode materials. We show that C60, unlike many other organic semiconductors, does not exhibit any intrinsic OMAR effect. However, we find that as soon as the carriers in C60 are brought in proximity with hydrogen-containing compounds, either in the form of a polymeric electrode, or side-chain substituents, a weak OMAR effect is observed. Next, we perform charge-induced absorption and electroluminescence spectroscopy in a polyfluorene organic magnetoresistive device. Our experiments allow us to measure the singlet exciton, triplet exciton and polaron densities in a live device under an applied magnetic field, and to distinguish between three models of OMAR. These models are based on different spin-dependent interactions, namely exciton formation, triplet exciton-polaron quenching and bipolaron formation. We show that the singlet exciton, triplet exciton and polaron densities and conductivity all increase with increasing magnetic field. Our data are inconsistent with the exciton formation and triplet-exciton polaron quenching models.

EFFECT OF Ba SUBSTITUTION ON ELECTRICAL TRANSPORT AND MAGNETORESISTANCE OF La1.2Sr1.8Mn2O7

2009 ◽  
Vol 23 (03) ◽  
pp. 447-460 ◽  
Author(s):  
Y. S. REDDY ◽  
P. KISTAIAH ◽  
C. VISHNUVARDHAN REDDY
Keyword(s):  
Magnetic Field ◽  
Low Temperature ◽  
Applied Magnetic Field ◽  
Electrical Transport ◽  
Sol Gel ◽  
Parent Compound ◽  
Temperature Dependent ◽  
Temperature Range ◽  
Anisotropic Lattice ◽  
Ba Substitution

Polycrystalline samples of double layered (DL) manganite system La 1.2( Sr 1-x Ba x)1.8 Mn 2 O 7(0.0≤×≤0.4) were prepared by the sol-gel method. The anisotropic lattice expansion is observed with the substitution of Ba 2+ into Sr 2+ sites. The electrical resistivity and magnetoresistance (MR) measurements were carried out over the temperature range 4.2 K–300 K. The substitution of Ba results in the suppression of T IM , insulator-to-metal transition temperature. A low temperature upturn of resistivity is seen in all the samples of the system, which is attributed to the spin-glass-like transition. The conduction mechanism above T IM is explained by Mott variable range hopping (VRH) mechanism. The variation of MR with temperature and applied magnetic field is discussed. From the temperature dependent MR curves, it is observed that the large MR values are present over a wide temperature range and the maximum MR values occur at [Formula: see text]. The x=0.4 sample exhibits ~31% of MR with the application of a mere 0.4 T field at 5 K, which accounts for ~35% enhancement of MR of parent compound (~23% of MR% at 0.4 T at 5 K). The MR — H data is fitted to the power law ρ = ρ0-αHn, and it is found that the low temperature MR varies as square root of the applied magnetic field, as expected in conventional metals.

The magnetostriction coefficients of nickel

1971 ◽  
Vol 326 (1564) ◽  
pp. 87-96 ◽  
Keyword(s):  
Magnetic Field ◽  
Magnetic Anisotropy ◽  
Temperature Dependence ◽  
Applied Magnetic Field ◽  
Strain Gauge ◽  
Room Temperature ◽  
Significant Contribution ◽  
Cubic Crystal ◽  
Anisotropy Coefficients

Measurements of the magnetostriction have been made, by means of the strain gauge technique, at room temperature, and at 79 and 5 K , and the results have been analysed in terms of the usual five-coefficient expression for a cubic crystal. The lack of parallelism between the applied magnetic field and the magnetization, due to the magnetic anisotropy, was allowed for by a method which enabled values of the anisotropy coefficients K 1 K 2 and K 3 to be deduced. The magnetostriction coefficients h 3 and h 5 are zero within the experimental uncertainties at all three temperatures and h 3 is certainly too small to produce any significant contribution to K 1 . The temperature dependence of h 1 and h 2 cannot be described by the theory of Callen & Callen (1963).

MICROWAVE ABSORPTION STUDIES ON HIGH-Tc SUPERCONDUCTORS AND RELATED MATERIALS VIII — ESR OF DPPH COATED ON BiSrCaCuO FILMS FABRICATED ON MgO (100) SUBSTRATES

1992 ◽  
Vol 06 (14) ◽  
pp. 879-889
Author(s):  
K. SUGAWARA ◽  
S. TANAKA
Keyword(s):  
Magnetic Field ◽  
Film Thickness ◽  
Temperature Dependence ◽  
Applied Magnetic Field ◽  
Zero Field ◽  
Magnetic Field Effects ◽  
High Tc Superconductors ◽  
Thick Sample ◽  
High Tc ◽  
Absorption Studies

ESR of DPPH coated on Bi - Sr - Ca - Cu - O films fabricated on MgO (100) substrates by MOCVD have been studied for samples with different thicknesses, 1000 Å and 100 Å. Temperature dependence of the ESR peak-to-peak linewidth, ΔH pp , revealed that ΔH pp , increases with film thickness. The excess ESR linewidth, δ (ΔH pp ) was also analyzed in terms of (1-t)α, with t=T/T c , giving for example α=4±1 for the 1000 Å thick sample. The ESR lineshapes were distorted by rotating the samples in applied magnetic fields. Severe distortion was found for the 1000 Å sample below about 30 K, but the distortion almost disappears at temperatures above 30 K. The applied magnetic field effects were also examined in both field-cooled and zero-field-cooled cases.

Magnetohydrodynamic Squeeze Films

1964 ◽  
Vol 86 (3) ◽  
pp. 441-444 ◽  
Author(s):  
D. C. Kuzma
Keyword(s):  
Magnetic Field ◽  
Film Thickness ◽  
Applied Magnetic Field ◽  
Conducting Fluid ◽  
Squeeze Film ◽  
Rectangular Plates ◽  
Circular Plates ◽  
Electrically Conducting ◽  
Electrically Conducting Fluid ◽  
Fluid Film Thickness

An analysis of hydrodynamic squeeze films is presented for the case of an electrically conducting fluid in the presence of a magnetic field. Circular plates and infinitely long rectangular plates are considered with a uniformly applied magnetic field. The relationships between fluid-film thickness and time are determined analytically and compared with the ordinary hydrostatic squeeze films. It is shown that the application of a magnetic field improves the squeeze-film action.

Comparison of magnetoelastic properties between the 〈110〉 oriented TbxDy1-xFe1.95 polycrystalline alloys with different Tb/Dy composition ratio under magnetomechanical loading

2014 ◽  
Vol 28 (27) ◽  
pp. 1450187
Author(s):  
Pei Zhao ◽  
You-He Zhou ◽  
Zhong-Zheng Lin
Keyword(s):  
Magnetic Field ◽  
Coercive Force ◽  
Compressive Stress ◽  
Applied Magnetic Field ◽  
Room Temperature ◽  
Hysteresis Loops ◽  
Polycrystalline Alloys ◽  
Magnetoelastic Properties ◽  
Engineering Designs ◽  
Magnetostriction Hysteresis

This paper presents comparison of magnetoelastic properties between the 〈110〉 oriented Tb x Dy 1-x Fe 1.95 polycrystalline alloys for x = 0.27, 0.3, 0.45 under coupled loading of magnetic field and compressive stress. The simultaneously measure are investigated for the magnetization and magnetostriction under applied magnetic field from -200 to 200 kA/m and compressive stress from 0 to 50 MPa along the rod axis at room temperature. The results show that, according to the increase of Tb concentration and compressive stress, the hysteresis, coercive force and magnetostriction hysteresis loops of Tb x Dy 1-x Fe 1.95 alloys increase rapidly and the distortion of the hysteresis loops occurs at higher compressive stress, especially Tb 0.45 Dy 0.55 Fe 1.95 alloys, while the maximum relative permeability of Tb x Dy 1-x Fe 1.95 alloys monotonously decrease. Meanwhile, the higher the Tb concentration the stronger is magnetostrictive "jump" effect. For these experimental results, the effect of compressive stress and Tb / Dy ratio on magnetoelastic properties of Tb x Dy 1-x Fe 1.95 alloys are coupling and remarkable. A tradeoff and optimization are very important for many engineering designs and applications.

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