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Studies of Structural, Magnetic and Dielectric
Properties of NdFe
0.5
Cr
0.5
O
3
Sharannia M. P, Santanu De, Nirmala R, Santhosh P. N*
Department of Physics, Indian Institute of Technology Madras, Chennai 600 036, India
* Corresponding author’s e-mail: santhosh@iitm.ac.in, Tel.: +91 044 2257 4882; Fax: +91 044 2257 4852
Abstract
NdFe
0.5
Cr
0.5
O
3
is synthesized by solid-state reaction in our search for novel perovskite based multiferroic materials. Rietveld refinement of X-ray diffraction pattern reveal Pnma space group at room temperature. The material shows an antiferromagnetic behavior with Néel temperature, T
N
~55 K, the result that can be explained within the framework of super-exchange rules. Studies of dielectric properties show a relaxor like transition around 460 K.
Keywords: Multiferroics, Perovskite.
behavior (Fig 2). The dielectric loss increases with increase in temperature that may be due to the increase in free charge carrier concentration.
0.4
0.3
0.2
0.1
NdFe0.5Cr0.5O3
H = 0.1 T
ZFC
FC
0.0
0 50 100 150 200 250 300
Temperature (K)
FIG. 1. Temperature dependence of ZFC and FC magnetization of NdFe
0.5
Cr
0.5
O
3
Introduction
Rare earth oxides with perovskite structure
(RBO
3
) show interesting magnetic and dielectric properties [1]. Orthoferrites (RFeO
3
) are mostly canted antiferromagnets [2]. Their magnetic properties can be enhanced by doping Cr at the B-site that introduces Cr-
O-Fe super-exchange ferromagnetic interaction.
Presence of a disorder in the B-site can make the magnetic interactions complex along with magnetic contribution from the A-site rare-earth ion.
Experimental Details
Polycrystalline NdFe
0.5
Cr
0.5
O
3
is synthesized by solid state reaction method. X-ray diffraction pattern confirms the phase purity of the sample. Rietveld refinement is done using General Structure Analysis
System (GSAS) [3]. Temperature and field variation of magnetization are studied from 20 K to 300 K and -1.5
T to 1.5 T respectively using Vibrating Sample magnetometer. Dielectric measurements are performed in the temperature range 123 K to 573 K and frequency range 1 Hz to 10 MHz using Broadband Impedance
Analyzer.
Results and Discussion
Rietveld refinement of X-ray diffraction pattern is done using GSAS. The refinement shows that
NdFe
0.5
Cr
0.5
O
3
has orthorhombic structure with Pnma space group at room temperature with lattice parameters a = 5.5449 Å, b = 7.7443 Å, and c = 5.4485 Å. Zero
Field Cooled (ZFC)
and Field Cooled (FC) magnetization data diverge at 265 K (Fig 1).
FC data show a cusp at around 55 K (Fig 1) suggesting an antiferromagnetic transition which has to be confirmed by further measurements. The variation of real part of dielectric constant with temperature shows peak shifting with increasing frequency, which indicates a relaxor like
6000
4500
3000
1500
0
6.3 kHz
12.3 kHz
47.4 kHz
182 kHz
500 kHz
1.4 MHz
5.3 MHz
NdFe0.5Cr0.5O3
100 200 300 400 500 600
Temperature (K)
FIG. 2. Temperature dependence of εʹ at various frequencies
Conclusion
Polycrystalline NdFe
0.5
Cr
0.5
O
3 is an antiferromagnetically ordered material that shows relaxor behaviour. This can be a potential magnetodielectric material.
Acknowledgement
PNS acknowledges CSIR for financial support.
References
[1] B. Lorenz et al., “Large magnetodielectric effects in orthorhombic HoMnO
3
and YMnO
3
”, Phys.Rev.B
, 70 ,
(2004), pp. 212412.
[2] W. Sławi´nski et al., “Spin reorientation and structural changes in NdFeO
3
”, J. Phys.: Condens.
Matter , 17, (2005), pp. 4605–4614.
[3] A. C. Larson and R. B. Von Dreele, “General structure analysis system (GSAS),” Los Alamos
National Laboratory Report LAUR 86-748 (2004).
