EPR study of Mn site substituted Pr based Doped Rare Earth Manganites

Abstract In this paper, we present the investigations of Electron Paramagnetic Resonance (EPR) on Mn site substituted Pr based Doped rare Earth Manganites i.e. Pr0.60Ca0.40MnO3 and Pr0.60Ca0.40Mn0.85Zn0.15O3. Changes in physical properties as lattice parameters, average valence of Mn site was observable of those manganites. X-ray diffraction pattern shows that both Pr0.60Ca0.40MnO3 and Pr0.60Ca0.40Mn0.85Zn0.15O3 have single phase and without the other secondary or impurity phase and indexed supported the Pbnm space group. The value of x in Pr0.60Ca0.40Mn1-xZnxO3 increases, the average valence V was increased except for a fixed composition, i.e. x remains unchanged, the average valence V was decreased as we go from less valency to high valency (i.e., from divalent to trivalent and from trivalent to tetravalent. The EDXS analysis of those materials shows good homogeneity, but there are experimental errors in composition. It is seen from the SEM images that is formed in different shape grains. The average grain sizes of the samples are different for Pr0.60Ca0.40MnO3 and Pr0.06Ca0.40Mn0.85Zn0.15O3 The paramagnetic resonance spectra parameters (effective g-factor, peak-to-peak line width) of Pr0.60Ca0.40MnO3 and Pr0.60Ca0.40Mn0.85Zn0.15O3.have been used to study the paramagnetic spin correlations and spin dynamics. As for Pr0.60Ca0.40MnO3 the line width becomes wider because of the contribution of small polaron jumping within the PM mechanism. However, as for Pr0.60Ca0.40Mn0.85Zn0.15O3 the broadening of EPR line-width is understood with the spin-lattice relaxation mechanism, g value decreased from 1.99 to 1.79. Therefore, the Zn dopant not solely changes the parent spin correlation in the PM regime however additionally suppresses the development of orbital ordering.

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Paramagnetic Resonance and Relaxation of Trivalent Rare-Earth Ions in Calcium Fluoride. II. Spin-Lattice Relaxation

Physical Review ◽

10.1103/physrev.134.a1504 ◽

1964 ◽

Vol 134 (6A) ◽

pp. A1504-A1516 ◽

Cited By ~ 80

Author(s):

R. W. Bierig ◽

M. J. Weber ◽

S. I. Warshaw

Keyword(s):

Rare Earth ◽

Calcium Fluoride ◽

Lattice Relaxation ◽

Rare Earth Ions ◽

Spin Lattice Relaxation ◽

Paramagnetic Resonance ◽

Spin Lattice ◽

Trivalent Rare Earth

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

Australian Journal of Physics ◽

10.1071/ph720107 ◽

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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