The Physical Properties of Submicron and Nano-Grained La0.7Sr0.3MnO3 and Nd0.7Sr0.3MnO3 Synthesised by Sol–Gel and Solid-State Reaction Methods

Abstract

La0.7Sr0.3MnO3 (LSMO) and Nd0.7Sr0.3MnO3 (NSMO) possess excellent colossal magnetoresistance (CMR). However, research work on the neodymium-based system is limited to date. A comparative study between LSMO and NSMO prepared by sol–gel and solid-state reaction methods was undertaken to assess their structural, microstructural, magnetic, electrical, and magneto-transport properties. X-ray diffraction and structure refinement showed the formation of a single-phase composition. Sol–gel-synthesised NSMO was revealed to be a sample with single crystallite grains and exhibited intriguing magnetic and electrical transport behaviours. Magnetic characterisation highlighted that Curie temperature (TC) decreases with the grain size. Strong suppression of the metal–insulator transition temperature (TMI) was observed and attributed to the magnetically disordered grain surface and distortion of the MnO6 octahedra. The electrical resistivity in the metallic region was fitted with theoretical models, and the conduction mechanism could be explained by the grain/domain boundary, electron–electron, and electron–magnon scattering process. The increase in the scattering process was ascribed to the morphology changes. Enhancement of low-field magnetoresistance (LFMR) was observed in nano-grained samples. The obtained results show that the grain size and its distribution, as well as the crystallite formation, strongly affect the physical properties of hole-doped manganites.

Characterisations of La-Sr-Mn-O (LSMO) Thin Film Fabricated by RF Sputtering

“…The MR graph exhibits two distinguishable parts, a steeper (H ≤ 2 kOe) descent followed by a more gradual (H ≥ 2 kOe) descent, known as extrinsic MR (or LFMR) and intrinsic MR, with the progression of the applied magnetic field. Extrinsic MR is contributed through a vital drop of resistance as a consequence of the spin-polarised tunnelling effect [39]. This is due to enhancement of hopping of e g electrons as randomly oriented spins in manganite grains are aligned towards the direction of a low magnetic field [40].…”

Investigation on the structural, magnetic, magnetocaloric and magnetotransport behaviour of La0.7Sr0.3MnO3 manganites synthesised by different routes

“…Several reports on the increase of resistivity with decreasing grain size have been published. 4,[31][32][33] Different theories have been proposed to explain the low-temperature transport properties like the double exchange (DE) and superexchange (SE) mechanism, Coulomb blockade effect, 34 electron-electron (e-e) interaction, 35,36 inter-granular spin-polarized tunnelling (ISPT), 37 Kondo-like mechanism, weak localization and quantum interference effects (QIEs). 35,36,38,39 It has been proposed that the parent compound LaMnO 3 (ABO 3 structure) is a charge transfer insulator and antiferromagnetic with Mn existing in the +3 oxidation state.…”

Structural and critical properties of Pr0.5Sr0.5MnO3 nanoparticle

“…Manganese-based perovskite system (called manganites with the general formula as R 1-x A x MnO 3 , where R = La, PrK and A = Ca, Sr, BaK) is one of the magnetocaloric materials of wide interest because they have some advantages (such as simple fabrication, stability under normal conditions, quite large electrical resistivity, and low costK) and exhibit interesting electrical and magnetic properties as well as rich phase diagram [1][2][3][4]. Partial substitution of the R/A position created a mixed valence of Mn ions (Mn 3+ and Mn 4+ ), which causes the appearance of double exchange interactions exhibiting ferromagnetic (FM) between the Mn 3+ -Mn 4+ pairs.…”