Magnetoresistance in Nd0.15Ca0.85MnO3
Lakshman Dhal1, R. Nirmala1*,P. N. Santhosh1, T. Geetha Kumary2, N. Shukla3and A. K. Nigam4
1
Department of Physics, Indian Institute of Technology Madras, Chennai 600 036, India
CMPD, Materials Science Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102, India
3
UGC-DAE CSR, Kalpakkam node, Kalpakkam 603 102
4
Tata Institute of Fundamental Research, Mumbai 400 005, India
*
E-mail: nirmala@iitm.ac.in
polaron hopping mechanism in the temperature range of
Abstract
Polycrystalline Nd0.15Ca0.85MnO3 oxide crystallizes in
160-200 K. The activation energies obtained from the
orthorhombic structure at room temperature (Space
fitting are 23.7 meV and 22.4 meV respectively for H =
group Pnma, No. 62). Electrical resistivity shows anomaly
0 T and H = 5 T. The sample shows negative
near the antiferromagnetic ordering temperature of 118 K
magnetoresistance where magnetoresistance is defined
(TN). Electrical resistivity data in the temperature range
200 K – 160 K indicate small polaron hopping behaviour.
as MR = [R(H) – R(0)]/ R(0). The MR value at 50 K
Nd0.15Ca0.85MnO3
exhibits
large
negative
increases up to ~ 89% in 10 T and then gradually
magnetoresistance of ~ 89% at 50 K in 10 T field.
saturates to ~ 100% in 15 T (Inset in Fig.1.)
2
Keywords: Magnetoresistance, electron doped manganite
Introduction
Electron doped manganites exhibit colossal
magnetoresistance for a narrow range of composition
and there are only few reports addressing this behavior
[1]. Several electron doped manganites exhibit magnetic
and structural phase separation [2]. They also show
charge and orbital ordering [3]. Often CMR effect in
electron doped manganites has been explained on the
basis of charge ordering [1]. These interesting and
unusual physical phenomena observed in electron doped
manganites have motivated further studies. Recent
studies on polycrystalline Gd0.15Ca0.85MnO3 have
revealed a complex antiferromagnetic transition at ~119
K in these samples [4]. In the present work, bulk
Nd0.15Ca0.85MnO3 has been synthesized and its electrical
resistivity and magnetoresistance properties are studied.
Fig.1. Electrical resistivity vs temperature of
Nd0.15Ca0.85MnO3 in 0 T and 5 T
(Inset: MR% vs Field H at 50 K)
Experimental details
Polycrystalline Nd0.15Ca0.85MnO3 was prepared
by solid state reaction. Phase purity of the sample was
verified by powder X-ray diffraction experiment at
room temperature. The stoichiometry was confirmed by
SEM-EDAX analysis. Temperature dependent electrical
resistivity and magnetoresistance were measured using a
Cryogenics 15 T system by conventional linear four
probe method.
Results and discussion
Room temperature crystal structure of
Nd0.15Ca0.85MnO3 is orthorhombic (Space group Pnma,
No. 62). Powder XRD data were analyzed by Rietveld
refinement techniques using General Structure Analysis
System (GSAS) program. Magnetization data reveal an
antiferromagnetic ordering ~118 K (TN) [Figure not
shown]. Temperature dependent resistivity (for H = 0 T
and 5 T field) shows a sudden slope change below ~ 110
K (Fig.1). The resistivity data were fitted with small
Conclusion
The electron doped manganite oxide
Nd0.15Ca0.85MnO3 has a strong slope change in electrical
resistivity near TN. A negative magnetoresistance of
about 89% is obtained at 50 K in 10 T field. Small
polaron hopping mechanism explains the electrical
resistivity behavior of Nd0.15Ca0.85MnO3 in the
temperature range of 160-200 K.
Acknowledgement
R. N. and T. G. K. thank UGC-DAE-CSR for project
support.
References
[1] Martin et al, J. Solid State Chem. 134 (1997) pp.
198-202
[2] Tong. et al, Appl. Phys. Lett. 93 (2008) pp.2025041-202504-3
[3] Sudheendra et al, J. Phys.: Condens. Matter 15
(2003) pp.895 – 905
[4] Dhal et al, Physica B, (2014) (In press)