scholarly journals Conduction Electron Scattering in Alloys

1986 ◽  
Vol 39 (4) ◽  
pp. 529 ◽  
Author(s):  
PL Rossiter
Keyword(s):  
Relaxation Time ◽  
Conduction Electron ◽  
Spin Glasses ◽  
Spin Fluctuation ◽  
Mean Free Path ◽  
Spin Fluctuations ◽  
Blocking Temperature ◽  
Magnetic Impurities ◽  
Magnetic Clusters ◽  
Electron Mean Free Path

The aim of this review is to present a simple physical picture which shows how the electrical resistivity of a system depends upon the spatial extent and lifetime of the scattering disturbance measured in relation to the conduction electron mean free path and relaxation time. The contribution from spin fluctuations associated with isolated magnetic impurities is discussed on the basis of this model and it is shown that at temperatures below the characteristic spin fluctuation temperature the impurity acts as though it were nonmagnetic. Some results are given for both 'Kondo' (Anderson) and exchange enhanced (Wolfi) systems. Spin glasses are also discussed and the resistivity behaviour is shown to result from a competition between the RKKY interaction and spin fluctuation effects. Ordered magnetic clusters are shown to be static for periods comparable with the conduction electron relaxation time, so that there is no resistivity anomaly expected at the superparamagnetic blocking temperature. The observed temperature dependence of the resistivity then follows simply from the change in magnetic correlations within the cluster.

Correlating Blocking Temperatures in Single Molecule Magnets with Raman Relaxation

2018 ◽  
Author(s):  
Marcus J. Giansiracusa ◽  
Andreas Kostopoulos ◽  
George F. S. Whitehead ◽  
David Collison ◽  
Floriana Tuna ◽  
...  
Keyword(s):  
Relaxation Time ◽  
Single Molecule ◽  
Energy Barrier ◽  
Thermal Relaxation ◽  
Relaxation Mechanism ◽  
Blocking Temperature ◽  
Single Molecule Magnets ◽  
Single Molecule Magnet ◽  
Key Parameter

We report a six coordinate DyIII single-molecule magnet<br>(SMM) with an energy barrier of 1110 K for thermal relaxation of<br>magnetization. The sample shows no retention of magnetization<br>even at 2 K and this led us to find a good correlation between the<br>blocking temperature and the Raman relaxation regime for SMMs.<br>The key parameter is the relaxation time (𝜏<sub>switch</sub>) at the point where<br>the Raman relaxation mechanism becomes more important than<br>Orbach.

scholarly journals Phonon residual resistance of pure crystals

2015 ◽  
Vol 29 (29) ◽  
pp. 1550206
Author(s):  
A. I. Agafonov
Keyword(s):  
Electric Field ◽  
Constant Electric Field ◽  
Finite Thickness ◽  
Mean Free Path ◽  
Residual Resistivity ◽  
Boltzmann Transport ◽  
Residual Resistance ◽  
Temperature Resistance ◽  
Electron Mean Free Path ◽  
The Ideal

In this paper, using the Boltzmann transport equation, we study the zero temperature resistance of perfect metallic crystals of a finite thickness d along which a weak constant electric field E is applied. This resistance, hereinafter referred to as the phonon residual resistance, is caused by the inelastic scattering of electrons heated by the electric field, with emission of long-wave acoustic phonons and is proportional to [Formula: see text]. Consideration is carried out for Cu, Ag and Au perfect crystals with the thickness of about 1 cm, in the fields of the order of 1 mV/cm. Following the Matthiessen rule, the resistance of the pure crystals, the thicknesses of which are much larger than the electron mean free path is represented as the sum of both the impurity and phonon residual resistances. The condition on the thickness and field is found at which the low-temperature resistance of pure crystals does not depend on their purity and is determined by the phonon residual resistivity of the ideal crystals. The calculations are performed for Cu with a purity of at least 99.9999%.

Magnetic study of Fe3O4/Ag nanoparticles

2018 ◽  
Vol 83 (1) ◽  
pp. 10402
Author(s):  
Janusz Typek ◽  
Nikos Guskos ◽  
Grzegorz Zolnierkiewicz ◽  
Zofia Lendzion-Bielun ◽  
Anna Pachla ◽  
...  
Keyword(s):  
Antibacterial Properties ◽  
Blocking Temperature ◽  
Precipitation Method ◽  
Magnetic Clusters ◽  
Mass Ratio ◽  
Three Samples ◽  
Two Samples ◽  
Magnetic Resonance Technique ◽  
Silver Nps ◽  
Multi Mode

Nanocomposites of Fe3O4 nanoparticles (NPs) impregnated with silver NPs display antibacterial properties and may be used in water treatment as disinfection agent. Three samples were synthesized: Fe3O4 NPs obtained by the precipitation method and additionally two samples with added silver NPs with mass ratio of Ag:Fe3O4 equal to 1:100 and 2:100. Magnetic properties of these samples were studied by SQUID magnetometry (in temperature range 2–300 K and magnetic fields up to 70 kG) and magnetic resonance technique at RT. Temperature dependence of dc susceptibility revealed the blocking temperature close to RT in all three samples and allowed to determine the presence of single or multi-mode distribution of NP sizes in a particular sample. Isothermal magnetisation measurements showed that the presence of silver NPs, especially those with smaller sizes, decreases the saturation magnetisation. The shape of ferromagnetic loop registered at T = 2 K was used to discuss the sizes of NP magnetic clusters in our samples. Conclusions obtained from analysis of the ferromagnetic resonance spectra were consistent with the propositions based on the magnetometric studies.

Interplay Between Thermoelectric and Thermionic Effects in Heterostructures

2000 ◽  
Author(s):  
Taofang Zeng ◽  
Gang Chen
Keyword(s):  
Film Thickness ◽  
Free Path ◽  
Thermionic Emission ◽  
Approximate Solutions ◽  
Mean Free Path ◽  
Boltzmann Transport ◽  
Thermoelectric Effects ◽  
Double Heterojunction ◽  
The Mean ◽  
Electron Mean Free Path

Abstract When electrons sweep through a double-heterojunction structure, there exist thermionic effects at the junctions and thermoelectric effects in the film. While both thermoelectric and thermionic effects have been studied for refrigeration and power generation applications separately, their interplay in heterostructures is not understood. This paper establishes a unified model including both thermionic and thermoelectric processes based on the Boltzmann transport equation for electrons, and the nonequilibrium interaction between electrons and phonons. Approximate solutions are obtained, leading to the electron temperature and Fermi level distributions inside heterostructures and discontinuities at the interfaces as a consequence of the highly nonequilibrium transport when the film thickness is much smaller than the electron mean free path. It is found that when the film thickness is smaller than the mean free path of electrons, the transport of electrons is controlled by thermionic emission. The coexistence of thermoelectric and thermionic effects may increase the power factor when the electron mean free path is comparable to the film thickness.

scholarly journals Control of Mooij correlations at the nanoscale in the disordered metallic Ta–nanoisland FeNi multilayers

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
N. N. Kovaleva ◽  
F. V. Kusmartsev ◽  
A. B. Mekhiya ◽  
I. N. Trunkin ◽  
D. Chvostova ◽  
...  
Keyword(s):  
Magnetic Moments ◽  
Mean Free Path ◽  
Dc Conductivity ◽  
Electronic Excitations ◽  
Many Body ◽  
Multilayered Structures ◽  
Multilayered Films ◽  
Disordered Metals ◽  
Electron Mean Free Path ◽  
Shed Light

AbstractLocalisation phenomena in highly disordered metals close to the extreme conditions determined by the Mott-Ioffe-Regel (MIR) limit when the electron mean free path is approximately equal to the interatomic distance is a challenging problem. Here, to shed light on these localisation phenomena, we studied the dc transport and optical conductivity properties of nanoscaled multilayered films composed of disordered metallic Ta and magnetic FeNi nanoisland layers, where ferromagnetic FeNi nanoislands have giant magnetic moments of 10$$^3$$ 3 –10$$^5$$ 5 Bohr magnetons ($$\mu _{\mathrm{B}}$$ μ B ). In these multilayered structures, FeNi nanoisland giant magnetic moments are interacting due to the indirect exchange forces acting via the Ta electron subsystem. We discovered that the localisation phenomena in the disordered Ta layer lead to a decrease in the Drude contribution of free charge carriers and the appearance of the low-energy electronic excitations in the 1–2 eV spectral range characteristic of electronic correlations, which may accompany the formation of electronic inhomogeneities. From the consistent results of the dc transport and optical studies we found that with an increase in the FeNi layer thickness across the percolation threshold evolution from the superferromagnetic to ferromagnetic behaviour within the FeNi layer leads to the delocalisation of Ta electrons from the associated localised electronic states. On the contrary, we discovered that when the FeNi layer is discontinuous and represented by randomly distributed superparamagnetic FeNi nanoislands, the Ta layer normalized dc conductivity falls down below the MIR limit by about 60%. The discovered effect leading to the dc conductivity fall below the MIR limit can be associated with non-ergodicity and purely quantum (many-body) localisation phenomena, which need to be challenged further.

Extended Dynamic Spin-Fluctuation Theory with Application to Iron

2012 ◽  
Vol 190 ◽  
pp. 55-58 ◽  
Author(s):  
B.I. Reser ◽  
N.B. Melnikov ◽  
Vladimir I. Grebennikov
Keyword(s):  
Phase Transition ◽  
Magnetic Properties ◽  
Green Function ◽  
Spin Fluctuation ◽  
Spin Fluctuations ◽  
Fluctuation Theory ◽  
Dynamic Spin ◽  
Discontinuous Phase ◽  
The Mean ◽  
Extended Dynamic

The problem of discontinuous phase transition in the dynamic spin-fluctuation theory is resolved by taking into account large anharmonic spin fluctuations and nonlocality of the mean Green function. The extended theory is applied to the calculation of magnetic properties of iron.

Sign in / Sign up

Export Citation Format

Share Document