Electrical transport properties and magnetic cluster glass behavior of Nd0.7Sr0.3MnO3 nanoparticles
TL;DR: In this article, the transport and magnetic properties of Nd07Sr03MnO3 nanoparticles were investigated by the sol-gel method and the results showed that resistivity increases with the decrease of the particle size due to the enhancement of the grain boundary effect.
Abstract: The transport and magnetic properties have been investigated in Nd07Sr03MnO3 nanoparticles prepared by the sol-gel method The resistivity (ρ) increases with the decrease of the particle size due to the enhancement of the grain boundary effect ρ(T) shows two distinct transitions for all the samples such as metal-insulator transition and transition due to the barrier caused by the grain boundary effect The thermopower (S) is found to be negative and at high temperature S follows the adiabatic small polaron hopping theory In the metallic region the spin wave contribution is found to be dominant in the temperature dependence of the thermopower The magnetoresistance (MR) of the ultrafine particles increases with the decrease of particle size indicating substantial contribution from the grain boundaries Spin polarized intergrain tunneling effect plays an important role in the MR of a smaller size particle, whereas in the case of samples of higher dimension spin fluctuation contributes predominantly The
Citations
More filters
TL;DR: In this paper, the temperature dependence of the ac magnetic susceptibility was measured at different frequencies and ac magnetic fields in the selected ranges of 40-1000-Hz and 80-800-A/m, respectively.
96 citations
TL;DR: In this article, the magnetic properties of compacted La0.8Ca0.2MnO3 manganite nanoparticles with average particle size of 18 and 70 nm and Curie temperatures TC 231 K and TC 261 K, respectively, have been investigated.
Abstract: Magnetic properties of compacted La0.8Ca0.2MnO3 manganite nanoparticles with average particle size of 18 and 70 nm and Curie temperatures TC 231 K and TC 261 K, respectively, have been investigated. The relative volume of the ferromagnetic phase has been estimated to be 52% for ensembles of 18 nm particles and 92% for 70 nm particles. It was found that applied hydrostatic pressure enhances TC of La0.8Ca0.2MnO3 nanoparticles at a rate dTC /dP 1.8– 1.9 K / kbar, independently on the average particle size. Pronounced irreversibility of magnetization below Tirr 208 K and strong frequency dependent ac susceptibility below TC for smaller 18 nm particles have been observed. 18 nm particles have also shown aging and memory effects in zero-field-cooled ZFC and field-cooled magnetization. These features indicate the appearance of spin-glasslike state, partially reminiscent the behavior of La1�xCaxMnO3 crystals, doped below the percolation threshold xxC = 0.225. In contrast, ensembles of larger 70 nm particles have shown insignificant irreversibility of magnetization only and no frequency dependence of ac susceptibility, similarly to the behavior of La1�xCaxMnO3 crystals with xxC. The temperature of the ZFC magnetization maximum for 18 nm particles decreases with increasing magnetic field and forms a critical line with an exponent 1.89 0.56. The results suggest that superspin-glass features in ensembles of interacting 18 nm particles appear along with superferromagnetic-like features.
86 citations
TL;DR: In this article, structural, magnetic, and electrical properties of the La0.8−xSmxSr0.2MnO3 manganites prepared by a solid-state reaction technique was studied systematically.
58 citations
TL;DR: In this article, the authors systematically outline some fundamentals and key experimental results concerning magnetic properties of perovskite manganites, focusing on magnetocaloric properties, pressure effect on magnetic properties, and magnetism of manganite nanoparticles.
Abstract: This chapter attempts to systematically outline some fundamentals and key experimental results concerning magnetic properties of perovskite manganites, focusing on (i) magnetocaloric properties, (ii) pressure effect on magnetic properties, and (iii) magnetism of manganite nanoparticles. Each family of manganites has unique properties that can be used as a way of tuning the optimum magnetocaloric response. The relatively easy possibility of tuning the Curie temperature of manganites is a key point in developing efficient magnetocaloric materials. The most interesting effects of applied external pressure observed for various classes of manganite systems, such as hole-doped manganites; parent, single-valent, and self-doped manganites; hexagonal manganites, near-half-doped manganites, electron-doped manganites, and manganite nanoparticles are reviewed. Some of the most relevant finite-size and surface effects on the magnetic properties of ferromagnetic and antiferromagnetic manganite nanoparticles are also discussed. New phenomena such as a suppression of charge/orbital ordering with decreasing particle size, collective states, and nonequilibrium dynamics in ensembles of antiferromagnetic manganite nanoparticles are presented.
57 citations
TL;DR: In this article, the authors determined the values of critical exponents of two polycrystalline samples (Nd1−xYx)0.7Sr0.3MnO3 (x = 0 and 0.07) from the magnetization data versus temperature and magnetic field, M(H, T), to learn about their magnetic and magnetocaloric (MC) properties.
44 citations
References
More filters
TL;DR: In this paper, the magnetic properties of the colossal magnetoresistance ferromagnet Ndo(0.7)Sr( 0.3)MnO(3) have been explored by ac-susceptibilities and dc-magnetization measurements.
Abstract: Dynamic magnetic properties of the colossal magnetoresistance ferromagnet Ndo(0.7)Sr(0.3)MnO(3) have been explored by ac-susceptibilities and dc-magnetization measurements. The system orders magnetically below T(c)approximate to 235 K with a large differe
74 citations
TL;DR: In this article, the effects of A-site rare earth elements on structural symmetry, magnetic and transport properties were systematically investigated, and it was shown that the tolerance factor t plays an important role in the structural distortion and grain boundary effect for the granular compounds.
55 citations
TL;DR: In this paper, the magnetic and transport properties of ultrafine La2/3Ca1/3MnO3 (LCMO) powders synthesized by mechanical alloying with a grain size of about 18 nm have been investigated.
Abstract: Magnetic and transport properties of ultrafine La2/3Ca1/3MnO3 (LCMO) powders synthesized by mechanical alloying with a grain size of about 18 nm have been investigated. It is found that the powder sample is superparamagnetic above 95 K. The blocking temperature (TB) obtained from the characteristic peak in the zero-field-cooled magnetization decreases with the measuring applied field, and can be well fitted by TB = aln (µ0H)-b. The spontaneous magnetization of the powder sample is only 38% of that in the corresponding bulk LCMO. Unlike conventional bulk LCMO, the powder compact is insulating from 5 K to 300 K. The low-temperature magnetoresistance (MR), defined as MR = ΔR/R(0) (R(0) being the zero-field resistance), is approximately 100% under a field of 6 T, much higher than that of the conventional bulk LCMO (50-60%). When the temperature is above TB, the low-field MR associated with the spin-polarized tunnelling between grains cannot be observed; however, the high-field MR increases linearly with the applied field. The small grain size and the surface layer in which many oxygen vacancies and defects induced by high-energy milling exist are suggested to be responsible for the present observations.
48 citations
TL;DR: In this paper, magnetization, resistance, and currentvoltage measurements have been performed in La05Sr05MnO3 compact prepared by pressing sol-gel nanoparticles (46 nm) at 723 K with a high pressure (4 GPa).
Abstract: Magnetization, resistance, and current-voltage (I-V) measurements have been performed in La05Sr05MnO3 compact prepared by pressing sol-gel nanoparticles (46 nm) at 723 K with a high pressure (4 GPa) The pressed compound orders ferromagnetically at 340 K (T-C) and has a substantial drop in the thermomagnetic curve below 158 K (T-DP) After undergoing a metal-to-semiconductor transition at 140 K (T-MS), the compound reenters into a strong semiconducting state below 60 K, demonstrating a charge localized behavior induced by the small grain rather than the magnetic disorder which is related with the frozen spin clusters below T-DP Instead of showing a feature near T-MS, the magnetoresistance (MR) ratio increases almost linearly with decreasing temperature The large low field MR corresponding to the sharp rise of magnetization is obtained at 5 K and, evidenced as the spin polarized intergrain tunneling (SPIT) effect by the nolinear I-V curve Although La05Sr05MnO3 has a relatively high T-C, the SPIT MR decays rapidly from 176% (5 K, 03 T) to 76% (150 K, 03 T), indicating that if trying to put the low field sensitivity of SPIT MR into application at room temperature, the selected compound having a higher T-C seems to be a prerequisite (C) 2000 American Institute of Physics [S0021-8979(00)92508-8]
40 citations
TL;DR: In this article, a new route to synthesize nanosized La0.75Ca0.25MnO3 perovskite complex oxides at a calcination temperature of 450 −6008C using the amorphous molecular alloy of La•Ca•Mn•DTPA as precursors.
36 citations