Sains Malaysiana 39(1)(2010): 93–98

 

Disorder Phenomena in Nd-doped (Pr1-xNdx)0.67Ba0.33MnO3 Manganites

(Fenomena Ketidak-tertiban dalam Sebatian Mangan (Pr1-xNdx)0.67Ba0.33MnO3 Berdop Nd

 

H. Abdullah*

Faculty of Engineering and Built Environment

Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor D.E.

 

S.A. Halim

Physics Department, Faculty of Sciences, Universiti Putra Malaysia

43400 UPM Serdang, Selangor D.E., Malaysia

 

Received: 14 October 2008 / Accepted: 13 January 2009

 

ABSTRACT

 

Polycrystalline samples of (Pr1-xNdx)0.67Ba0.33MnO3 with x = 0.0, 0.167, 0.33, 0.5, 0.67, 0.833, and 1.0 have been prepared using the solid state reaction. The samples were calcined at 900oC for 12 hours, pelletized and sintered at 1300oC for 24 hours. The structures were investigated via X-ray diffraction (XRD) method. XRD patterns showed orthorhombic distorted perovskite structures. The scanning electron microscopy (SEM) micrographs showed the disorder of the structure in all substitutions. This influenced the value of the magnetoresistance (MR). The MR effects are measured using the four point probe technique with a magnetic field of B <= 1T at temperatures of 90, 100, 150, 200, 250, 270 and 300 K. Overall, the MR increased as the temperature decreased. All doping concentrations gave a small variation range (~10% to ~56%). The highest MR value of 56.5 % is observed at 100 K for a sample with x = 1.0. The influence of disorder on the magnetoresistance in (Pr1-xNdx)0.67Ba0.33MnO3 manganites at low temperatures was also discussed in this paper.

Keywords: Disordered structure; low-field magnetoresistance; orthorhombic

 

ABSTRAK

Sample polihablur (Pr1-xNdx)0.67Ba0.33MnO3 dengan x = 0.0, 0.167, 0.33, 0.5, 0.67, 0.833 dan 1.0) telah disediakan melalui tindak balas keadaan pepejal. Sampel telah dipanaskan pada 900oC selama 12 jam, dipeletkan dan dipanaskan pada 1300oC selama 24 jam. Strukturnya dikaji melalui kaedah pembelauan sinar-X (XRD). Corak-corak XRD menunjukkan struktur herotan ortorombus. Mikrograf-mikrograf bagi mikroskop imbasan elektron (SEM) menunjukkan struktur yang tak teratur yang terlibat dalam setiap penggantian. Ini juga mempengaruhi nilai magnetorintangan (MR). Kesan-kesan magnetorintangan (MR) diukur menggunakan teknik empat titik penduga, pada medan magnet B <= 1T pada 90, 100, 150, 200, 250, 270 dan 300 K. MR meningkat bila suhu yang dikenakan menurun. Semua kepekatan dopan memberi jurang perubahan yang kecil (~10% hingga ~56%). Nilai MR yang tertinggi adalah 56.5% diperhatikan pada 100 K untuk sampel x = 1.0. Pengaruh ketidak-tertiban terhadap magnetorintangan dalam sistem sebatian mangan (Pr1-xNdx)0.67Ba0.33MnO3 pada suhu rendah juga dibincangkan.

 

Kata kunci: Ketidak-tertiban struktur; medan-rendah magnetorintangan; ortorombus

 

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Zener, 1951. Interaction between the d-shells in the transition metals. II. Ferromagnetic compounds of Manganese with perovskite structure. Phys. Rev. 82: 403-405.

 

*Corresponding author; email: huda@vlsi.eng.ukm.my