Nonlinear dielectric and magnetic relaxation after a sudden change of applied field

2001 ◽  
Vol 115 (10) ◽  
pp. 4444-4449 ◽  
Author(s):  
B. U. Felderhof ◽  
R. B. Jones
Keyword(s):  
Magnetic Relaxation ◽  
Applied Field ◽  
Sudden Change ◽  
Nonlinear Dielectric

Magnetorheological Measurements in Suspensions of Magnetic Nanoparticles

2005 ◽  
Author(s):  
A. Chaves ◽  
F. Gutman ◽  
C. Rinaldi
Keyword(s):  
Magnetic Relaxation ◽  
Applied Field ◽  
Flow Problem ◽  
Ultrasonic Method ◽  
Azimuthal Velocity ◽  
Field Amplitude ◽  
Geometric Aspect ◽  
Regular Perturbation ◽  
Aspect Ratios ◽  
Annular Gap

We report measurements of the torque required to restrain a polycarbonate spindle surrounded by ferrofluid in a cylindrical container and subjected to the rotating field generated by a two-pole magnetic induction motor stator, as a function of applied field amplitude and frequency, and for various values of the geometric aspect ratios of the problem. Simultaneously, an ultrasonic method was used to measure the azimuthal velocity profiles in the ferrofluid contained in the annular gap of our apparatus. These measurements are compared to a rigorous regular perturbation solution in the small parameter Ωτ (Ω = frequency and τ = ferrofluid magnetic relaxation time) of the ferrohydrodynamic flow problem in the zero spin viscosity and linear magnetization limits.

On the theory of the nonlinear effect in polar liquids

1978 ◽  
Vol 56 (2) ◽  
pp. 216-225 ◽  
Author(s):  
Constantino Grosse ◽  
Pedro Brito
Keyword(s):  
Dipole Moment ◽  
Nonlinear Effect ◽  
Spherical Cavity ◽  
Applied Field ◽  
Polar Liquids ◽  
Nonlinear Dielectric ◽  
Average Value ◽  
Molecular Moment ◽  
Dipolar Potential ◽  
Weak Fields

It is shown that in order to relate the permittivity ε = ε0[1–λE2] of a nonlinear dielectric with molecular parameters using Onsager's formalism, the condition to be used is that the average value of the dipolar potential outside the cavity and with an applied field must vanish. Consequently, the potential for a rigid dipole in a spherical cavity filled up with a continuum ε∞ and surrounded by a nonlinear dielectric immersed in a strong applied field are calculated both inside and outside. The average value of the external dipole moment is deduced from the torque exerted by the field outside the cavity on the sources of the applied field.The expression thus obtained for the parameter λ leads to values that are always positive and slightly smaller than those corresponding to earlier studies. The expression deduced for the permittivity in weak fields ε0 introduces a correction to Onsager's equation consisting of a factor multiplying the square of the molecular moment. In contradiction with recent results by other authors, this factor is always less than 1 and its value is of the order of 0.9.

Nonlinear Dielectric Relaxation of Mn Doped Polycrystalline (Ba,Sr)TiO3 Thin Films Over the Temperature Range of 4.2 - 473 K

1998 ◽  
Vol 541 ◽  
Author(s):  
J.D. Baniecki ◽  
R.B. Laibowitz ◽  
T.M. Shaw ◽  
P.R. Duncombe ◽  
D.E Kotecki ◽  
...  
Keyword(s):  
Thin Films ◽  
Dielectric Relaxation ◽  
Applied Field ◽  
Equivalent Circuit Model ◽  
Nonlinear Dielectric ◽  
Nonlinear Relaxation ◽  
Temperature Range ◽  
Reciprocal Temperature ◽  
Mn Doped ◽  
Relaxation Component

AbstractWe have investigated the dielectric relaxation currents of Mn doped polycrystalline Ba0.7Sr0.3TiO3 (BSTO) thin films as a function of applied electric field and temperature (4.2 - 473 K). The dielectric relaxation currents followed a power law time dependence, J(t) = Jot-n, over the entire temperature range. Plots of log(Jo) vs. reciprocal temperature were not linear and showed slopes approaching values of 0.35 eV at high temperatures which rapidly decreased to 0.25 meV at lower temperatures. The relaxation currents were found to be nonlinear with applied field. The observed nonlinearity of the field dependence of the relaxation currents can be understood in terms of the nonlinear relaxation component of the total capacitance. An equivalent circuit model for a paraelectric BSTO thin film capacitor is presented and possible polarization mechanisms are briefly discussed.

MAGNETIC RELAXATION EFFECTS IN ZERO FIELD COOLED Y–Ba–Cu–O

1990 ◽  
Vol 04 (03) ◽  
pp. 473-478 ◽  
Author(s):  
S. K. HASANAIN ◽  
A. MUMTAZ ◽  
T. ALI ◽  
M. HUSAIN ◽  
G. S. BHATTI
Keyword(s):  
Relaxation Process ◽  
Exponential Type ◽  
Magnetic Relaxation ◽  
Applied Field ◽  
Onset Time ◽  
Zero Field ◽  
Two Stage ◽  
Field Reversal ◽  
Type Function ◽  
Relaxation Effects

Results of the magnetic relaxation in 1:2:3 superconductors initiated by a very slow field reversal, are reported. We find that the relaxation at earlier times follows a stretched exponential type function, while at longer times it has a logarithmic behaviour. The onset time of ln t behaviour depends on the applied field. The data is interpreted in terms of a two-stage relaxation process.

Dinuclear Lanthanide–Carboxylate Compounds: Field-Induced Slow Relaxation of Magnetization for Dysprosium(III) Analogue

2015 ◽  
Vol 68 (3) ◽  
pp. 488 ◽  
Author(s):  
Yi-Lei Li ◽  
Qing-Yan Liu ◽  
Cai-Ming Liu ◽  
Yu-Ling Wang ◽  
Ling Chen
Keyword(s):  
Energy Barrier ◽  
Magnetic Relaxation ◽  
Applied Field ◽  
Antiferromagnetic Interaction ◽  
Slow Relaxation ◽  
Phen Ligand ◽  
Exponential Factor ◽  
Coordination Environment ◽  
Carboxylate Groups ◽  
Slow Magnetic Relaxation

Three chiral dinuclear lanthanide compounds, Ln2(µ2-L)4(L)2(phen)2 (Ln = Dy (1), Gd (2), and Er (3); phen = 1,10-phenanthroline), have been synthesized using the (S)-(+)-2-(6-methoxy-2-naphthyl)propionic acid (HL) ligand. The two lanthanide centres in compound Ln2(µ2-L)4(L)2(phen)2 are bridged by four carboxylate groups to give a dinuclear Ln2(µ2-L)4 core. The square antiprismatic coordination environment for each lanthanide centre is further completed by a chelating carboxylate group from another L– ligand and two nitrogen atoms from the phen ligand. A weak antiferromagnetic interaction between the two GdIII ions is observed in compound 2. The Dy analogue displays field-induced slow magnetic relaxation behaviour with an effective energy barrier Ueff/k of 17.24(2) K and a pre-exponential factor τ0 of 2.7(1) × 10–6 s. However, no slow relaxation phenomenon was observed for the Er derivative even in the presence of 2 kOe applied field.

The value of Electron Microscope studies of imperfect natural diamonds

1990 ◽  
Vol 48 (4) ◽  
pp. 194-195
Author(s):  
J C Walmsley ◽  
A R Lang
Keyword(s):  
Electron Microscope ◽  
Classification Scheme ◽  
Natural Diamond ◽  
Sudden Change ◽  
Growth Conditions ◽  
Diamond Growth ◽  
Major Constituent ◽  
Natural Diamonds ◽  
Type Ia ◽  
Platelet Defects

Interest in the defects and impurities in natural diamond, which are found in even the most perfect stone, is driven by the fact that diamond growth occurs at a depth of over 120Km. They display characteristics associated with their origin and their journey through the mantle to the surface of the Earth. An optical classification scheme for diamond exists based largely on the presence and segregation of nitrogen. For example type Ia, which includes 98% of all natural diamonds, contain nitrogen aggregated into small non-paramagnetic clusters and usually contain sub-micrometre platelet defects on {100} planes. Numerous transmission electron microscope (TEM) studies of these platelets and associated features have been made e.g. . Some diamonds, however, contain imperfections and impurities that place them outside this main classification scheme. Two such types are described.First, coated-diamonds which possess gem quality cores enclosed by a rind that is rich in submicrometre sized mineral inclusions. The transition from core to coat is quite sharp indicating a sudden change in growth conditions, Figure 1. As part of a TEM study of the inclusions apatite has been identified as a major constituent of the impurity present in many inclusion cavities, Figure 2.

Correlating the axial Zero Field Splitting with the slow magnetic relaxation in GdIII SIMs

2021 ◽  
Author(s):  
Júlia Mayans ◽  
Albert Escuer
Keyword(s):  
Magnetic Relaxation ◽  
Zero Field ◽  
Zero Field Splitting ◽  
Field Splitting ◽  
Slow Magnetic Relaxation

A possible relation between the value of the axial Zero Field Splitting and the occurrence of field-induced slow magnetic relaxation has been established for a new gadolinium(iii) compound.

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