Structural, Electron Spin Resonance and Magnetic
Properties of La0.37(Bi, Sm)0.30Ca0.33MnO3
Ramesh Ade and R. Singh*
School of Physics, University of Hyderabad, Central University P.O., Hyderabad 500046, India.
Corresponding author`s email: rssp@uohyd.ernet.in , Ph: 040-2313 4321 , Fax: 040-2301 0227.
Abstract
In the present work we report the structural, electron
spin resonance (ESR) and magnetic properties of La0.37(Bi,
Sm)0.30Ca0.33MnO3. The evolution of different coexisting
magnetic phases with Bi and Sm doping are ascribed to the
lattice distortion caused by the size mismatch of the A-site
cations.
decrease in the magnetization, TC and evolution of spin
or cluster glass state compared to La0.67Ca0.33MnO3 are
ascribed to the lattice distortion caused by the size
mismatch of the A-site cations by Bi and Sm ion doping
[1, 3]. Doping suppresses the ferromagnetic (FM)
double exchange (DE) interactions.
Key words: Sol-gel synthesis, Electron spin resonance,
Magnetization, Double exchange and Phase separation.
Introduction
Manganese oxides with ABO3 perovskite
structure have been extensively studied since the
discovery of colossal magnetoresistance. There are few
reports on the effect of dopants at La site in Lamanganite [1, 2]. In the present work we report the
detailed structural, electron spin resonance (ESR) and
magnetization measurements of La0.37Bi0.30Ca0.33MnO3
(B30) and La0.37Sm0.30Ca0.33MnO3 (S30) manganites
synthesized by sol-gel method.
Fig.1: ESR spectra for B30 (A) and S30 (B).
Results and discussions
Rietveld refinement of X- ray diffraction data
for all the samples confirms the single phase Pnma
space group with orthorhombic structure. Fig.1 shows
the ESR spectra for the samples at various temperatures.
Fig.2 (A) shows the peak to peak linewidth (ΔH) of
ESR signal as a function of temperature (T). ΔH
decreases with decreasing temperature from 453 K,
reaches a minimum at ~ 230 and 150 K for B30 and S30
respectively. It increases with further decrease in
temperature. Fig.2 (B) shows magnetization (M) as a
function of temperature, both in zero fields cooled
(ZFC) and field cooled (FC) modes in an applied field
of 500 Oe. B30 shows two magnetic transitions (Curie
temperature, TC), at ~166 and 218 K. Whereas S30
shows only one transition (TC) at ~ 100 K. The peak
observed at 168 and 223 K in an upper shoulder of ESR
signal (Fig.1 A) in the low field region confirms the
magnetic transitions observed in M versus (vs) T plots.
The sharp rise in M and the peak (spin freezing
temperature, Tf) observed in ZFC curve indicate the
evolution of spin or cluster glass state with doping. The
Fig.2: ΔH vs T and M vs T plots of B30 (a) and S30 (b)
Acknowledgement
Ramesh Ade is grateful for the award of UGCSRF from CSIR India.
References
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