Anomalous Behavior in Spin Dependent Tunnel Junctions

1997 ◽  
Vol 475 ◽  
Author(s):  
C. L. Platt ◽  
B. Dieny ◽  
A.E. Berkowitz
Keyword(s):  
Magnetic Field ◽  
Low Temperature ◽  
Barrier Layer ◽  
Tunnel Junction ◽  
Applied Magnetic Field ◽  
Low Temperatures ◽  
Tunnel Junctions ◽  
Anomalous Behavior ◽  
Field Transition

ABSTRACTSpin dependent tunneling has been investigated in tunnel junctions composed of a variety of materials. The best results thus far have been with either HfO2 or MgO as the barrier layer using CoFe, Fe, or Co as the magnetic electrodes. The maximum magnetoresistive (MR) response of these junctions has been at low temperatures on the order of 30% in HfO2 and 20% in MgO. We have also observed a variety of anomalous behavior in some of our tunnel junctions at low temperature. These include MR effects dependent on the angle of orientation of the tunnel junction in the applied magnetic field, transition fields greater than lOkOe, and negative MR effects on the order of 2%.

THE LOW-TEMPERATURE SPECIFIC HEAT OF U(Pt, Pd)3

1993 ◽  
Vol 07 (01n03) ◽  
pp. 14-17
Author(s):  
H. P. VAN DER MEULEN ◽  
J. J. M. FRANSE ◽  
A. DE VISSER
Keyword(s):  
Magnetic Field ◽  
Low Temperature ◽  
Specific Heat ◽  
Applied Magnetic Field ◽  
Low Temperatures ◽  
Single Crystalline ◽  
Normal Part ◽  
Electron Contribution ◽  
Heavy Electron ◽  
Low Temperature Specific Heat

Specific-heat measurements on single-crystalline samples of U ( Pt 1− x Pd x )3 ( x = 0.00, 0.05 and 0.10) reveal anomalously large values for c/T at low temperatures. The data for UPt 3 have previously been analyzed by making use of the enhanced value of the low-temperature Grüneisen parameter. By this analysis, the heavy-electron contribution to the specific heat has been separated from the normal part that is largely due to the phonon term. Taking this latter term to be the same for all three compounds, the heavy-electron contribution has been evaluated for temperatures below 20 K. This contribution is compared with a spin-1/2 Kondo-type of specific heat. The resulting curves for the x = 0.00 and x = 0.10 alloys are very similar and mainly differ in the temperature at which the maximum is found. The effect of an applied magnetic field within the hexagonal plane, however, shifts the maximum to lower temperatures for x = 0.00 whereas for x = 0.10 a shift towards higher temperatures is found.

LOW-TEMPERATURE NORMAL-STATE HALL EFFECT IN HIGH-TcBi2Sr2-xLaxCuO6+δ REVEALED BY 60 T MAGNETIC FIELDS

2002 ◽  
Vol 16 (20n22) ◽  
pp. 3171-3174
Author(s):  
F. F. BALAKIREV ◽  
J. B. BETTS ◽  
G. S. BOEBINGER ◽  
S. ONO ◽  
Y. ANDO ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Low Temperature ◽  
Carrier Concentration ◽  
Hall Coefficient ◽  
Normal State ◽  
Ground State ◽  
Low Temperatures ◽  
Optimal Doping ◽  
Underdoped Sample ◽  
Additional Support

We report low-temperature Hall coefficient in the normal state of the high-Tc superconductor Bi 2 Sr 2-x La x CuO 6+δ. The Hall coefficient was measured down to 0.5 K by suppressing superconductivity with a 60 T pulsed magnetic field. The carrier concentration was varied from overdoped to underdoped regimes by partially substituting Sr with La in a set of five samples. The observed saturation of the Hall coefficient at low temperatures suggests the ability to extract the carrier concentration of each sample. The most underdoped sample exhibits a diverging Hall coefficient at low temperatures, consistent with a depletion of carriers in the insulating ground state. The Hall number exhibits a sharp peak providing additional support for the existence of a phase boundary at the optimal doping.

Point-contact spectroscopy probing the NbSe3 CDW gap in different crystallographic orientations

2002 ◽  
Vol 12 (9) ◽  
pp. 119-122
Author(s):  
A. A. Sinchenko ◽  
P. Monceau
Keyword(s):  
Magnetic Field ◽  
Low Temperature ◽  
Applied Magnetic Field ◽  
Energy Gap ◽  
Point Contact ◽  
Point Contacts ◽  
Energy Gaps ◽  
Current Voltage ◽  
Current Voltage Characteristics ◽  
Crystallographic Orientations

We have measured the differential current-voltage characteristics of normal metal-NbSe3 direct point contacts (without insulating barrier) formed along different crystallographic orientations under applied magnetic field with different orientations. At low temperature two energy gaps, $\Delta_{p1}$ and $\Delta_{p2}$, corresponding to the high and the low-temperature CDW were observed simultaneously as a singulanty of the excess resistance which is attributed to an analog of Andreev reflection, in which the incident electron reflects on the Peierls energy gap barriers with its charge unchanged. An applied magnetic field up to 8.5 T does not lead to a change in the density of states and in the Peierls energy gaps, suggesting that the large magnetoresistance observed in NbSe3 might not result from the change in the CDW order parameter with magnetic field but rather from the increase of scattering of non-condensed to CDW carriers.

Low-temperature Preparation of Crystallized Zirconia Films by ECR Plasma MOCVD

2005 ◽  
Vol 890 ◽  
Author(s):  
Hiroshi Masumoto ◽  
Takashi Goto
Keyword(s):  
Magnetic Field ◽  
Low Temperature ◽  
Low Temperatures ◽  
Monoclinic Zirconia ◽  
High Quality ◽  
Ion Chamber ◽  
Ecr Plasma ◽  
Low Temperature Preparation ◽  
Oxide Ion ◽  
Zirconia Films

ABSTRACTIt is known that zirconia has excellent thermal and chemical stability, and oxide ion conduction. Therefore, YSZ is expected to be used as oxide ion conducting materials, optical mirror materials, catalytic materials and heat-resistant materials. Zirconia films have been fabricated by PVD (ex. sputtering and laser-ablation), chemical vapor deposition (CVD) and sol-gel methods. CVD is capable to prepare high quality zirconia films with excellent conformal coverage; however, deposition temperature of conventional CVD was usually high than PVD. On the other hand, an electron cyclotron resonance (ECR) plasma is high-activity plasma and high quality crystalline films can be obtained at low temperature by using ECR plasma. In the present study, zirconia thin films were prepared at low temperatures on quartz, polycarbonate and polyimide substrates by ECR plasma MOCVD.Zr-hexafluoroacetylacetonato solution was used as a precursor. The source, which was placed in a glass bubbler, was carried into a reactor by Ar gas. A microwave (2.45 GHz, 500 W) was introduced into the ion chamber through a rectangular wave guide. A magnetic field (875 Gauss) was applied to the ion chamber to satisfy the ECR condition. A mirror-type magnetic field (450 Gauss at the substrate stage) was applied in order to raise a plasma density, which results in an increase of the deposition rates of films. Substrate temperature (Ts) was from 30 to 700 C by water-cooling holder and infrared lamp heater. Microwave power was changed from 0 to 900 W. The deposition time was from 30 to 120 minutes.Cubic, monoclinic and tetragonal zirconia films were obtained over Ts=400 C, and cubic and monoclinic zirconia films were obtained below Ts= C. Cubic and monoclinic zirconia films were also obtained at no heating. The deposition rate increased from 10 to 20 nm/min with increasing Ts from no heating to 600 C. Crystallized zirconia films were obtained on polycarbonate and polyimide substrates at no heating. The ECR plasma was significantly effective to prepare crystallized zirconia films at low temperatures.

HOPPING CONDUCTIVITY IN ONE-DIMENSIONAL Ca3Co2O6 SINGLE CRYSTAL

2002 ◽  
Vol 16 (20n22) ◽  
pp. 3289-3292 ◽  
Author(s):  
J. M. BROTO ◽  
B. RAQUET ◽  
H. RAKOTO ◽  
M. N. BAIBICH ◽  
S. LAMBERT ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Single Crystal ◽  
Applied Magnetic Field ◽  
Low Temperatures ◽  
Electronic Conductivity ◽  
Magnetic Ordering ◽  
One Dimensional ◽  
Coulomb Gap ◽  
Hopping Conductivity ◽  
Magneto Resistance

We studied the electronic conductivity of the quasi-one dimensional Ca3Co2O6 single crystal. The results evidence a VRH conductivity with temperature-induced crossover between 1D (intra-chain) and 3D transport and the opening of a Coulomb gap in the d bands. At low temperatures, an applied magnetic field induces a large negative magneto-resistance (MR) independent from the 3D magnetic ordering. Both spin-dependent hopping and field-induced suppression of the Coulomb gap are discussed.

scholarly journals Controllable two- vs three-state magnetization switching in single-layer epitaxial Pd1-xFex films and epitaxial Pd0.92Fe0.08/Ag/Pd0.96Fe0.04 heterostructure

2021 ◽  
Author(s):  
Igor Yanilkin ◽  
Amir Gumarov ◽  
Gulnaz Gizzatullina ◽  
Roman Yusupov ◽  
Lenar Tagirov
Keyword(s):  
Magnetic Field ◽  
Low Temperature ◽  
Applied Magnetic Field ◽  
Magnetization Reversal ◽  
Easy Axis ◽  
Magnetic State ◽  
Magnetic Moments ◽  
Single Layer ◽  
Wide Range ◽  
Ferromagnetic Layers

We have investigated the low-temperature magnetoresistive properties of a thin epitaxial Pd0.92Fe0.08 film at different directions of the current and the applied magnetic field. The obtained experimental results are well described within an assumption of a single-domain magnetic state of the film. In a wide range of the appled field directions, the magnetization reversal proceeds in two steps via the intermediate easy axis. An epitaxial heterostructure of two magnetically separated ferromagnetic layers, Pd0.92Fe0.08/Ag/Pd0.96Fe0.04, was synthesized and studied with the dc magnetometry. Its magnetic configuration diagram has been constructed and the conditions have been determined for a controllable switching between stable parallel, orthogonal, and antiparallel arrangements of magnetic moments of the layers.

scholarly journals Теплоемкость скандобората NdSc-=SUB=-3-=/SUB=-(BO_3)-=SUB=-4-=/SUB=-

2021 ◽  
Vol 63 (12) ◽  
pp. 2226
Author(s):  
Е.В. Еремин ◽  
Н.Д. Андрюшин ◽  
И.А. Гудим ◽  
М.С. Павловский ◽  
В.Р. Титова
Keyword(s):  
Magnetic Field ◽  
Heat Capacity ◽  
Low Temperature ◽  
Single Crystals ◽  
Temperature Region ◽  
Applied Magnetic Field ◽  
Molar Heat Capacity ◽  
Group Method ◽  
Lattice Contribution ◽  
Einstein Model

Single crystals of trigonal neodymium scandoborate NdSc3(BO3)4 were grown by the group method from a solution-melt based on bismuth trimolybdate. The molar heat capacity C(T) was studied in the temperature range 2-300 K and magnetic fields up to 9 T. The experimental curve was approximated by the combined Debye-Einstein model. The lattice contribution was determined from ab-initio calculations. Schottky anomaly was observed in the low-temperature region C(T) with the applied magnetic field.

HIGH-FIELD TRANSPORT PROPERTIES OF T'-Ln2-xCexCuO4 (Ln=Nd, Pr, La)

2002 ◽  
Vol 16 (20n22) ◽  
pp. 3216-3219 ◽  
Author(s):  
T. SEKITANI ◽  
N. MIURA ◽  
M. NAITO
Keyword(s):  
Magnetic Field ◽  
Low Temperature ◽  
Magnetic Fields ◽  
Transport Properties ◽  
Normal State ◽  
Low Temperatures ◽  
High Field ◽  
Magnetic Moments ◽  
Negative Magnetoresistance ◽  
High Magnetic Fields

We report low-temperature magnetotransport in the normal state of the electron-doped superconductors, Nd 2-x Ce x CuO 4, Pr 2-x Ce x CuO 4, and La 2-x Ce x CuO 4, by suppressing the superconductivity with high magnetic fields. The normal state ρ-T curve shows an up-turn at low temperatures, which has a log T dependence with saturation at lowest temperatures. The up-turn is gradually suppressed with increasing magnetic field, resulting in negative magnetoresistance. We discuss these findings on the basis of the Kondo scattering originating from the magnetic moments of Cu 2+ ions.

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.

Sign in / Sign up

Export Citation Format

Share Document