Measuring acoustic mode resonance alone as a sensitive technique to extract antiferromagnetic coupling strength

2015 ◽  
Vol 92 (6) ◽  
Author(s):  
Yajun Wei ◽  
Peter Svedlindh ◽  
Mikhail Kostylev ◽  
Mojtaba Ranjbar ◽  
Randy K. Dumas ◽  
...  
Keyword(s):  
Coupling Strength ◽  
Acoustic Mode ◽  
Antiferromagnetic Coupling ◽  
Sensitive Technique

scholarly journals Systematic Raman study of optical phonons in RBa2Cu3O6+δ ( R=Y , Dy, Gd, Sm, Nd): Antiferromagnetic coupling strength versus lattice parameters

2019 ◽  
Vol 99 (9) ◽  
Author(s):  
Silvia Müllner ◽  
Wayne Crump ◽  
Dirk Wulferding ◽  
Benjamin P. P. Mallett ◽  
Peter Lemmens ◽  
...  
Keyword(s):  
Coupling Strength ◽  
Lattice Parameters ◽  
Antiferromagnetic Coupling ◽  
Optical Phonons ◽  
Raman Study

Studies of Exchange Coupling in Fe (001) Whisker/Cr/Fe Structures using BLS and Rheed Techniques.

1993 ◽  
Vol 313 ◽  
Author(s):  
B. Heinrich ◽  
M. From ◽  
J.F. Cochran ◽  
L. X. Liao ◽  
Z. Celiński ◽  
...  
Keyword(s):  
Coupling Strength ◽  
Exchange Coupling ◽  
High Energy ◽  
Variable Number ◽  
Antiferromagnetic Coupling ◽  
Iron Film ◽  
First Principles Calculations ◽  
Iron Whisker ◽  
Short Period ◽  
Coupling Strengths

ABSTRACTThe conditions for an almost perfect growth of smooth Cr (001) films on an iron whisker substrate have been investigated by means of reflection high energy electron diffraction (RHEED). The exchange interaction between 20 Monolayer thick Fe (001) films separated from a bulk whisker Fe (001) substrate by a variable number of Cr (001) Monolayers (ML) has been investigated by means of Brillouin light scattering experiments (BLS). These experiments show unambiguously that the exchange coupling strength between the iron film and the iron whisker can be described by a short wavelength oscillatory term superposed on a slowly varying antiferromagnetic background. The BLS data enabled one to separate the bilinear and the biquadratic contributions to the antiferromagnetic exchange coupling terms. Both the bilinear and the biquadratic coupling strengths exhibited a short period oscillatory dependence on the Cr interlayer thickness (∼2 Monolayers). Maxima in the bilinear antiferromagnetic coupling strength occur for an odd number of Cr Monolayers. This observation is not in agreement with first principles calculations. The first phase inversion has been found to occur between 4 and 5 ML of Cr.

Bls Studies of Exchange Coupling in The Iron Whisker/Cr/Fe System

1995 ◽  
Vol 384 ◽  
Author(s):  
J.F. Cochran ◽  
K. Totland ◽  
B. Heinrich ◽  
D. Venus ◽  
S. Govorkov
Keyword(s):  
Thin Film ◽  
Coupling Strength ◽  
Kerr Effect ◽  
Exchange Coupling ◽  
Molecular Beam ◽  
Growth Conditions ◽  
Antiferromagnetic Coupling ◽  
Ferromagnetic Coupling ◽  
Film Magnetization

ABSTRACTBrillouin light scattering (BLS) and magneto-optic Kerr effect have been carried out on a series of specimens consisting of a Fe(001) whisker substrate upon which thin Cr(001) and Fe(001) layers have been deposited by means of molecular beam epitaxy in ultrahigh vacuum. The Fe film was 20 monolayers (ML) thick, and the Cr(001) films were grown having various thicknesses. It is demonstrated that BLS thin film frequencies measured in the saturated magnetic state with the thin film magnetization parallel with the applied magnetic field can be used to obtain the exchange coupling strength between the thin film and whisker magnetizations both for antiferromagnetic coupling and for ferromagnetic coupling, provided that the ferromagnetic coupling is not too strong. It is also shown that the coupling strength is extremely sensitive to the quality of the chromium growth: a small deterioration in the growth conditions has been found to reduce the exchange coupling by nearly a factor of two.

Coupling in Fe(2 ML)/V(y ML) and Fe(2 ML)/V(y ML)/Fe(3 ML)/V(y ML) (y ≥ 4) superlattices

Open Physics ◽  
2007 ◽  
Vol 5 (1) ◽  
Author(s):  
Karen Paul
Keyword(s):  
Coupling Strength ◽  
Antiferromagnetic Coupling ◽  
Physical Parameters

AbstractFe(2 ML)/V(y ML) and interleaved Fe(2 ML)/V(y ML)/Fe(3 ML)/V(y ML) superlattice systems with spacer thicknesses, y, (4 ≤ y ≤ 17) were investigated macro-magnetically to estimate the coupling strength and the magnetoresistance in these materials, and particularly in the antiferromagnetically coupled monolayers. The results from the magnetic and magnetoresistive measurements indicate that adding one monolayer of Fe increases the antiferromagnetic coupling and the magnetoresistivity ratio from 0.0075 mJ/m2 at 20 K and 2 % at 10 K for Fe(2 ML)/V(y ML), to 0.05 mJ/m2 and 2.5 % for Fe(2 ML)/V(y ML)/Fe(3 ML)/V(y ML) at the same temperatures. Both systems exhibit in-plane magnetic and magnetoresistive isotropy, therefore the increase of the conferred physical parameters is attributed mainly to the stresses at the interface as governing mechanisms over the magnetoelastic forces.

scholarly journals Manipulation of Time- and Frequency-Domain Dynamics by Magnon-Magnon Coupling in Synthetic Antiferromagnets

2021 ◽  
Vol 8 (1) ◽  
pp. 7
Author(s):  
Xing Chen ◽  
Cuixiu Zheng ◽  
Sai Zhou ◽  
Yaowen Liu ◽  
Zongzhi Zhang
Keyword(s):  
Phase Difference ◽  
Coupling Strength ◽  
Phase State ◽  
Acoustic Mode ◽  
Antiferromagnetic Resonance ◽  
Micromagnetic Simulations ◽  
Resonance Modes ◽  
Ferromagnetic Layers ◽  
Domain Dynamics ◽  
Crossing Point

Magnons (the quanta of spin waves) could be used to encode information in beyond Moore computing applications. In this study, the magnon coupling between acoustic mode and optic mode in synthetic antiferromagnets (SAFs) is investigated by micromagnetic simulations. For a symmetrical SAF system, the time-evolution magnetizations of the two ferromagnetic layers oscillate in-phase at the acoustic mode and out-of-phase at the optic mode, showing an obvious crossing point in their antiferromagnetic resonance spectra. However, the symmetry breaking in an asymmetrical SAF system by the thickness difference, can induce an anti-crossing gap between the two frequency branches of resonance modes and thereby a strong magnon-magnon coupling appears between the resonance modes. The magnon coupling induced a hybridized resonance mode and its phase difference varies with the coupling strength. The maximum coupling occurs at the bias magnetic field at which the two ferromagnetic layers oscillate with a 90° phase difference. Besides, we show how the resonance modes in SAFs change from the in-phase state to the out-of-phase state by slightly tuning the magnon-magnon coupling strength. Our work provides a clear physical picture for the understanding of magnon-magnon coupling in a SAF system and may provide an opportunity to handle the magnon interaction in synthetic antiferromagnetic spintronics.

Magnetic Supramolecular Grid Structures: Intramolecular Coupling of Four Separate Spins

1997 ◽  
Vol 488 ◽  
Author(s):  
O. Waldmann ◽  
J Hassmann ◽  
R. Koch ◽  
P. Müller ◽  
G. S. Hanan ◽  
...  
Keyword(s):  
Coupling Strength ◽  
Antiferromagnetic Coupling ◽  
Metal Centers ◽  
Tetranuclear Complexes

AbstractThe magnetization of novel tetranuclear supramolecular grid structures and their mononuclear analogues was measured. In the tetranuclear complexes with Co2+ or Ni2+ ions an intramolecular antiferromagnetic coupling of the four metal centers is observed. The isotropic coupling strength was determined to be J = -8 K for the Ni2+ grids, and J = -2 K for the Co2+ grids.

Henderson Hasselbalch Relationship and Weak Acid Titration

2019 ◽  
Author(s):  
Marc Blétry
Keyword(s):  
Theoretical Framework ◽  
Weak Acid ◽  
Acid Base ◽  
Sensitive Technique ◽  
Chemistry Students ◽  
Advanced Students ◽  
Acid Titration ◽  
Acid Base Titration ◽  
Analytical Expressions

Henderson-Hasselbalch relation is generally the simplified theoretical framework used to introduce students to acid-base titration. However, it is not always valid and its limitations should be made clear to chemistry students. The appropriate parameter to evaluate its validity is K a /C 0 , in connection with Ostwald dilution law. For more advanced students, it is possible to deduce analytical expressions that always fit accurately acid-base titrations and allow an evaluation of Henderson Hasselbalch relation. Gran plot appears as a particularly sensitive technique to the breakdown of Henderson Hasselbalch relation.

Nutrient Removal in Small Wastewater Treatment Plants

1990 ◽  
Vol 22 (3-4) ◽  
pp. 211-216
Author(s):  
Niels Skov Olesen
Keyword(s):  
Wastewater Treatment ◽  
Nitrogen Removal ◽  
Nutrient Removal ◽  
Phosphorus Removal ◽  
Wastewater Treatment Plants ◽  
Ferrous Sulphate ◽  
Practical Solution ◽  
Sensitive Technique ◽  
Pumping Station ◽  
Denitrification Reactor

In some areas of Denmark nutrient removal is required even for very small wastewater plants, that is down to 500 pe (pe = person equivalents). The goal for the removal is 80% removal of nitrogen and 90% removal of phosphorus, or in terms of concentrations: 8 mg nitrogen/l and 1.2 mg phosphorus/l. The inlet concentrations are typically 40 mg N/l and 10 mg P/l. The paper presents the results from two such plants with a capacity of 800 pe. Phosphorus removal is made by simultaneous precipitation with ferrous sulphate. Nitrogen removal is carried out using the recirculation method. Both plants were originally rotor aerated oxidation ditches. They have been extended with a denitrification reactor and a recirculation pumping station. At present both plants have been in activity for about 3 years and with satisfactory results. Average concentrations of nitrogen (summer) and phosphorus is 7 mg/l and 0.9 mg/l respectively. Nitrogen removal seems to be a practical solution on these small plants. It is,though, sensitive to temperature and highly oxidized rain water. Phosphorus removal seems to be an easily run and relatively non-sensitive technique at least when using simultaneous precipitation.

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