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].

scholarly journals Study of Magnetic Property of Sn Doped Ni-Zn-Fe Nanoparticles

2014 ◽  
Vol 2014 ◽  
pp. 1-4 ◽  
Author(s):  
B. S. Tewari ◽  
Archana Dhyani ◽  
S. K. Joshi ◽  
Santosh Dubey ◽  
Kailash Pandey
Keyword(s):  
Average Particle Size ◽  
Lattice Relaxation ◽  
Lattice Relaxation Time ◽  
Spin Lattice Relaxation ◽  
Epr Spectra ◽  
Spin Interaction ◽  
Average Particle ◽  
Band Frequency ◽  
Spin Lattice ◽  
Dominant Process

The Ni0.6+xZn0.4SnxFe2-2xO4 (x=0.00 to 0.04) samples were prepared by solution route technique. These samples were characterized by XRD and EPR spectra at X-band frequency (~9.2 GHz). The XRD spectra of these ferrites confirm the formation of spinel structure. The average particle size calculated by using Scherrer’s formula was found to be of the order of 24.7 nm. The EPR spectra of these ferrites are mainly due to Fe3+ ions. Fe2+ ions have very short spin-lattice relaxation time and therefore EPR spectra of Fe2+ could be observed only at very low temperature. This fact is also supported by the isomer shift values of these ferrites obtained from Mössbauer spectroscopy. The variation of geff and ΔHPP with Sn4+ concentration is attributed to the variation of superexchange interaction. Moreover in this system the dominant process of relaxation is the spin lattice relaxation rather than the spin-spin interaction.

An Effect of Deuteration on Ion Motions and Hydrogen Bondings in Guanidinium Tetrafluoroborate

1992 ◽  
Vol 47 (7-8) ◽  
pp. 803-806 ◽  
Author(s):  
J. Wąsicki ◽  
M. Grottel ◽  
A. Kozak ◽  
Z. Pająk
Keyword(s):  
Relaxation Time ◽  
Activation Parameters ◽  
Lattice Relaxation ◽  
Lattice Relaxation Time ◽  
Spin Systems ◽  
Spin Lattice Relaxation ◽  
Spin Lattice ◽  
Relaxation Effects ◽  
Wide Range ◽  
Hydrogen Bondings

Abstract The fluorine spin-lattice relaxation time as well as NMR second moment for perdeuterated guanidinium tetrafluoroborate were studied over a wide range of temperature. An analytical solution of a set of coupled differential equations describing the time variation of nuclear magnetisations for four unlike spin systems was applied to analyse all cross-relaxation effects in the compound. Activation parameters EFa = 19.3 kJ/mole and τFU= 9 • 10"14 s for the isotropic anion reorientation were derived. A coupling of rotational modes of cation and anion was found. Significant lowering of the melting point explained by a weakening of the hydrogen bonds involves diminishing of the ion activation energies due to the large positive isotope effect

SPIN–LATTICE RELAXATION TIME OF Fe3+ ION

1964 ◽  
Vol 42 (4) ◽  
pp. 583-594 ◽  
Author(s):  
M. P. Madan
Keyword(s):  
Relaxation Time ◽  
Lattice Relaxation ◽  
Lattice Relaxation Time ◽  
Spin Lattice Relaxation ◽  
Direct Process ◽  
Phonon Interaction ◽  
Crystal Axis ◽  
Spin Lattice Relaxation Time ◽  
Spin Lattice ◽  
Relaxation Effects

The spin–lattice relaxation time T1 of Fe3+ ions in iron–rubidium alum [RbAl(SO4)2∙12H2O], in rutile [TiO2], and in potassium cobalticyanide [K3CO(CN)6] has been measured in the temperature range 1.6 °K to 4.2 °K at a frequency of 9400 Mc by the pulse saturation technique. For Fe3+ in rubidium alum, it is found that for crystals having a nominal concentration of 1% and lower the variation of relaxation time with temperature is of the form [Formula: see text]; for higher concentrations the variation is of the form [Formula: see text]. Cross-relaxation effects are noticed for higher concentrations at all settings of crystal orientations. For Fe3+ in rutile on the average, the relaxation time is approximately inversely proportional to temperature, thus indicating the presence of a direct process. There is no significant change in the relaxation time, when the angle of the applied magnetic field with the crystal axis is varied. For Fe3+in K3Co(CN)6, above 2.8 °K, it is found that the relaxation time is proportional to T−8; this is consistent with a two-phonon interaction process (Raman). It is not believed that at the lowest temperature used in this experiment relaxation is taking place through a single-phonon process (direct).

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.

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.

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