scholarly journals The Effect of a Temperature Gradient in a Single Crystal on E.P.R. Line Shape and Width

1972 ◽  
Vol 25 (1) ◽  
pp. 107
Author(s):  
YH Ja
Keyword(s):  
Line Width ◽  
Line Shape ◽  
Order Approximation ◽  
Lattice Relaxation ◽  
Lattice Relaxation Time ◽  
Spin Lattice Relaxation ◽  
Spin Hamiltonian ◽  
Paramagnetic Resonance ◽  
Spin Lattice ◽  
Crystal Field Parameters

Temperature is an important parameter in electron paramagnetic resonance experiments and studies at different temperatures can give a great deal of useful information about the investigated spin system and its interaction with its environment. Generally speaking, all of the parameters in the spin-Hamiltonian, such as the g factor, hyperfine interaction constants, etc., are independent of the temperature to a first-order approximation, but the line shape, line width, and spin-lattice relaxation time are quite sensitive to temperature changes. However, e.p.r. studies in many natural or synthetic crystals with very low concentrations of paramagnetic impurity-ions indicate that the line width ?H and the line shape are virtually independent of the temperature T (provided T is not too low), while the crystal-field parameters in the spin-Hamiltonian, such as D and E, show a considerable variation with temperature. The former comes about because the line widths in such cases depend mainly on the mosaic structure (Shaltiel and Low 1961; Wenzel and Kim 1965) and the local distortions (mechanical or electrical strains) (Wenzel and Kim 1965) of the crystal lattice which are practically independent of the temperature. The latter is mainly due to the shrinkage or expansion of the crystal which changes the interactions between the paramagnetic ion and its neighbouring ions.

OPTICAL FARADAY ROTATION STUDIES OF PARAMAGNETIC RESONANCE IN NEODYMIUM ETHYLSULPHATE

1963 ◽  
Vol 41 (1) ◽  
pp. 33-45 ◽  
Author(s):  
K. E. Rieckhoff ◽  
D. J. Griffiths
Keyword(s):  
Steady State ◽  
Lattice Relaxation ◽  
Lattice Relaxation Time ◽  
Spin Lattice Relaxation ◽  
Spin Interaction ◽  
Spatial Gradient ◽  
Constant Field ◽  
Paramagnetic Resonance ◽  
Spin Lattice ◽  
Relaxation Effects

The magneto-optical Faraday effect was used to measure the saturation of the spin levels in concentrated neodymium ethylsulphate in both steady-state and pulsed microwave resonance experiments at liquid helium temperatures. The steady-state experiments yielded the paramagnetic resonance spectrum consisting of a main triplet and an extensive hyperfine structure. The line positions are explained in terms of the known spin Hamiltonian of the diluted salt and spin–spin interaction between nearest neighbors. An asymmetry of the line shape was observed for sufficiently low temperatures in qualitative agreement with existing theories. Measurements of saturation s versus microwave power P at constant field and temperature were made and yielded the relationship [Formula: see text] for s > 10%. The steady-state experiments also revealed the existence of a spatial gradient in the saturation across the sample.The pulsed experiments gave the spin–lattice relaxation time τ as a function of magnetic field H at various temperatures. At 4.2 °K, τ was found to be independent of H and of the order of 11 msec for fields from 800 to [Formula: see text], while at temperatures below 2 °K, τ was found to be strongly field-dependent, indicating the importance of cross-relaxation effects at temperatures [Formula: see text].

Studies of Rubberlike Polymers by Nuclear Magnetism

1955 ◽  
Vol 28 (2) ◽  
pp. 480-487
Author(s):  
V. R. Honnold ◽  
F. McCaffrey ◽  
B. A. Mrowca
Keyword(s):  
Natural Rubber ◽  
Line Width ◽  
Average Molecular Weight ◽  
Lattice Relaxation ◽  
Lattice Relaxation Time ◽  
Spin Lattice Relaxation ◽  
Chain Molecules ◽  
Polypropylene Oxide ◽  
Spin Lattice ◽  
Curing Of Polymers

Abstract The actual width of the proton resonance line in uncured natural rubber has been determined at room temperature to be 0.06 gauss. Curing of polymers increases the line width at a given temperature. The small increase in natural rubber is possibly compatible with a physical bonding rather than the usually assumed cross-linking. For a butadiene-styrene copolymer, the increase of line width due to cure is somewhat larger. Carbon-black loading increases the line width to a lesser degree than does cure. This is compatible with the concept of physical bonding between the blacks and the polymer chain molecules. Variations of line width caused by changes in chemical composition and copolymerization were also investigated. Polypropylene and polypropylene oxide of roughly the same average molecular weight are compared. The polypropylene oxide exhibits a greater degree of “rotation” about its C—O bonds than polypropylene does about its C—C bonds. Two butadiene-acrylonitrile copolymers also have been studied as a function of temperature. Finally, spin-lattice relaxation time vs. temperature studies are reported for a butadiene-acrylonitrile copolymer and for raw Butyl, over the temperature range from −50° to 70° C. Estimates of the magnitude of the barriers hindering “rotation” are made.

Host Spin-Lattice Relaxation Narrowing in Pr2Co3(NO3)12 · 24 H2O: Mn2+ \ Gd3+ Single Crystals

1980 ◽  
Vol 35 (12) ◽  
pp. 1308-1312 ◽  
Author(s):  
Vimal Kumar Jain
Keyword(s):  
Single Crystals ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Single Type ◽  
Spin Hamiltonian ◽  
Paramagnetic Resonance ◽  
Spin Lattice ◽  
X Band ◽  
Hamiltonian Parameters ◽  
Electron Paramagnetic

Abstract Electron paramagnetic resonance of Mn2+ and Gd3+ in single crystals of Pr2Co3(NO3)12 · 24 H2O has been studied at X-band at 305 and 77 K. Mn2+ substitutes at two types of Co2+ sites whereas Gd3 substitutes at the single type of Pr3+ site in the lattice. The spin-Hamiltonian parameters have been evaluated. Observation of resolved Mn2+ and Gd3+ spectra at 305 K and their broadening on lowering the temperature are discussed in terms of host spin-lattice relaxation narrowing.

The nature of the crystalline fields in Ti 3+ alum

1960 ◽  
Vol 255 (1280) ◽  
pp. 145-151 ◽  
Keyword(s):  
Lattice Relaxation ◽  
Lattice Relaxation Time ◽  
Magnetic Behaviour ◽  
Spin Lattice Relaxation ◽  
Orbital Method ◽  
Paramagnetic Resonance ◽  
Crystalline Field ◽  
Susceptibility Data ◽  
Spin Lattice ◽  
Resonance Data

A theory of susceptibility for titanium caesium alum is given. The crystalline field in this alum is treated on the molecular orbital method of Stevens and others, as the usual electrostatic field theory is found to fail to explain the magnetic behaviour. Experimental susceptibility data between 300 and 100°K as well as the paramagnetic resonance data at 2·5°K can all be accounted for satisfactorily by assuming that the trigonal field splitting changes from 800 to ≈ 170 cm -1 , with temperature, which is also indicated by the large observed increase in the spin-lattice relaxation time from 300 to 1·2°K.

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