Journal ArticleDOI

# Study of irradiation induced changes in La0.7Pb0.3MnO3

01 Jun 2003-Radiation Measurements (Pergamon)-Vol. 36, Iss: 1, pp 689-693

TL;DR: In this paper, a typical giant magnetoresistive (GMR) sample viz. La 0.7 Pb 0.3 MnO 3 has been irradiated by 50 MeV Li 3+ ion beam.

AbstractA typical giant magnetoresistive (GMR) sample viz. La 0.7 Pb 0.3 MnO 3 has been irradiated by 50 MeV Li 3+ ion beam. Irradiated samples have been studied from the measurement of resistivity down to 77 K in presence of 1.5 T magnetic field. Although magnetoresistance is not maximum at T im as the samples are polycrystalline, however, a small peak like structure has been found around T im . The peak is most prominent for maximum fluence.

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TL;DR: In this article, the effects of ion irradiation on the transport properties of polycrystalline La0.5Pb 0.5Mn1−xCrxO3 (x = 0.075 and 0.15) samples have been studied by means of the temperature and magnetic field dependent resistivity measurements.
Abstract: Polycrystalline La0.5Pb0.5Mn1−xCrxO3 (x = 0.075 and 0.15) samples have been irradiated with 50 MeV Li3+ ions with different fluences and the effects on the transport properties have been studied by means of the temperature and magnetic field dependent resistivity measurements. Due to Li3+ ion irradiation, the resistivity increases and the metal–insulator transition temperature (Tmi) decreases. At low temperatures (below Tmi), a dominant contribution of the electron–magnon scattering process is observed for all the irradiated and unirradiated samples. The low temperature resistivity behavior as well as the magnetoresistance is modified due to irradiation. The changes in the magnetotransport properties due to irradiation have been compared with the changes caused due to Mn site substitution.

16 citations

Journal ArticleDOI

TL;DR: In this article, the low temperature (below the metal-insulator transition temperature Tim) resistivity and magnetoresistance (MR) behavior of 50 MeV Li3+ beam irradiated La 0.7Pb0.3MnO3 for three different fluences were reported.
Abstract: We report the low temperature (below the metal–insulator transition temperature Tim) resistivity and magnetoresistance (MR) behavior of 50 MeV Li3+ beam irradiated La0.7Pb0.3MnO3 for three different fluences. Ion beam irradiation causes a decrease of Tim leading to the increase of insulating regime. Resistivity data of the unirradiated as well as irradiated samples fitted well with an equation of the form ρ = ρ0 + ρ2.5T2.5 which indicates predominant contribution from the electron–magnon interaction (second term). The temperature dependent MR data of samples irradiated with different ion fluences follow the simple relation [MR = a + b/(T + C)] showing appreciable effect of radiation on the parameters a, b and C. The physical significance of the radiation effect on these parameters is not yet very clear.

14 citations

Journal ArticleDOI

TL;DR: In this paper, the effect of electron beam irradiation on structural, electrical and thermal properties of Gd0.5Sr 0.5MnO3 manganites was investigated.
Abstract: We present systematic studies on the effect of electron beam irradiation on structural, electrical and thermal properties of Gd0.5Sr0.5MnO3 and Dy0.5Sr0.5MnO3 manganites. The XRD patterns and Rietveld analysis show that the samples remain single phased even after they undergo electron beam irradiation. Both the series of the samples Gd0.5Sr0.5MnO3 and Dy0.5Sr0.5MnO3 show insulating trends in their temperature dependent electrical resistivity, ρ(T) behavior. The resistivity data for both the series of samples (pristine as well as irradiated) indicate that the small polaron hopping model is valid in high temperature region; on contrary, variable range hopping model governs the low temperature regime. Magnetic studies demonstrate that the Neel temperatures of pristine and irradiated samples of Gd0.5Sr0.5MnO3 and Dy0.5Sr0.5MnO3 do not change appreciably when they are subjected to irradiation. Thermo-electrical power is observed to increase with irradiation in Gd0.5Sr0.5MnO3 samples, whereas for Dy0.5Sr0.5MnO3 samples a decrease in thermo-electric power is seen when the samples are irradiated.

13 citations

Journal ArticleDOI

TL;DR: In this article, the effect of 90 MeV heavy ion irradiation on the surface morphology, transport and magnetic properties of La0.9Pb0.1MnO3 (LPMO) single crystals has been reported.
Abstract: Effect of 90 MeV heavy-ion irradiation on the surface morphology, transport and magnetic properties of La0.9Pb0.1MnO3 (LPMO) single crystals has been reported. It was found that at low ion-fluence the metal-insulator transition temperature (T-MI) increases by similar to 3 K and the Curie temperature (T-c) increases similar to 4 K, and the resistivity decreases as the irradiation increases up to 1 x 10(12). However, we have observed that the T-MI reduces with an increase in resistivity for the fluence of 1 X 10(13). These results correlate well with the irradiation induced strain, creation of point defect and grain boundaries in the crystals. (C) 2009 Elsevier B.V. All rights reserved.

9 citations

Journal ArticleDOI
TL;DR: In this paper, the effect of disorder on Bi-2212 type high Tc superconducting and LCMO type CMR oxide materials has been investigated and results have been discussed in the light of their intrinsic granular nature.
Abstract: Present report deals with the effect of disorder on Bi-2212 type high Tc superconducting and LCMO type CMR oxide materials. Ion irradiation (50 MeV Li3+ beam) creates high level of disorder in the superconducting system and as a result increase of room temperature resistivity (ρ300) has been observed. Radiation induced point defects cause an increased dρ/dT in the metal-like regime of Bi-2212. Similar increase of dρ/dT in the FM (ferromagnetic and metal-like) state has also been found in LCMO system. Enhancement of metal-like behavior is unusual in the sense that a simultaneous decrease of Tmi (metal–insulator transition temperature for LCMO) or Tc (superconducting transition temperature for Bi-2212) due to irradiation has also been observed. Effect of the defects incorporated by other means like variation of heat treatment and ion irradiation has been investigated for a better understanding on the electrical transport in these complex materials. Results have been discussed in the light of their intrinsic granular nature.

4 citations

##### References
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Journal ArticleDOI
TL;DR: In this paper, it was shown that both electrical conduction and ferromagnetic coupling in these compounds arise from a double exchange process, and a quantitative relation was developed between electrical conductivity and the Ferromagnetic Curie temperature.
Abstract: Recently, Jonker and Van Santen have found an empirical correlation between electrical conduction and ferromagnetism in certain compounds of manganese with perovskite structure. This observed correlation is herein interpreted in terms of those principles governing the interaction of the $d$-shells of the transition metals which were enunciated in the first paper of this series. Both electrical conduction and ferromagnetic coupling in these compounds are found to arise from a double exchange process, and a quantitative relation is developed between electrical conductivity and the ferromagnetic Curie temperature.

4,843 citations

BookDOI
01 May 1998
TL;DR: A review of the topics of colossal magnetoresistance, charge ordering and related phenomena exhibited by oxides, and contributions covering the present status of the subject can be found in this paper,.
Abstract: An aspect of metal oxides, colossal magnetoresistance exhibited by certain manganese oxides, in particular rare-earth manganates of perovskite structure, has received much attention in recent years. Some of these oxides show 100 per cent magnetoresistance, and have potential for technological applications. This text begins with a review of the topics of colossal magnetoresistance, charge ordering and related phenomena exhibited by oxides, and presents contributions covering the present status of the subject.

1,069 citations

Journal ArticleDOI
, S. Piñol1
TL;DR: The amplitude $\ensuremath{\rho}(T,H)$ and temperature ${T}_{M}$ and CMR are found to be controlled by the radius of the lanthanide $({L}^{3+})$ which modifies the bending of the Mn-O-Mn bond.
Abstract: The amplitude $\ensuremath{\Delta}\ensuremath{\rho}(T,H)/\ensuremath{\rho}$ and temperature ${T}_{M}$, where the colossal magnetoresistance (CMR) response of ${L}_{1\ensuremath{-}x}{\mathrm{Ca}}_{x}{\mathrm{MnO}}_{3}$ manganites are maximum, are found to be controlled by the radius of the lanthanide $({L}^{3+})$ which modifies the bending of the Mn-O-Mn bond. Increasing the bond distortion lowers ${T}_{M}$ and enhances $\ensuremath{\Delta}\ensuremath{\rho}(T,H)/\ensuremath{\rho}$. Enhanced CMR arises from (1) a shift to lower temperatures of ${T}_{M}$, (2) a reduced mobility of the doping holes, and (3) an increase of the coupling between itinerant and localized electrons. The resistivity $\ensuremath{\rho}\left(H\right)$ follows an $\ensuremath{\approx}{\mathrm{BM}}^{2}\left(H\right)$ law and the parameter $B$ is also tuned by the Mn-O-Mn bond angle. The narrowing of the electronic bandwidth is the fundamental parameter controlling the observed CMR.

406 citations

Journal ArticleDOI
M. McCormack
TL;DR: In this article, it was shown that the peak magnetoresistance peak occurs not at the temperature of magnetic transition but at a temperature where the magnetization is still substantial, the spin disorder scattering is not likely to be the main mechanism in these highly magnetoresistive films.
Abstract: Colossal magnetoresistance with more than a thousandfold change in resistivity (ΔR/RH=127 000% at 77 K, H=6 T) has been obtained in epitaxially grown La‐Ca‐Mn‐O thin films. This magnetoresistance value is about three orders of magnitude higher than is typically seen in the giant‐magnetoresistance‐type metallic, superlattice films. The temperature of peak magnetoresistance is located in the region of metallic resistivity behavior. As the magnetoresistance peak occurs not at the temperature of magnetic transition but at a temperature where the magnetization is still substantial, the spin‐disorder scattering is not likely to be the main mechanism in these highly magnetoresistive films. The peak can be shifted to near room temperature by adjusting processing parameters. Near‐room‐temperature ΔR/RH values of ∼1300% at 260 K and ∼400% at 280 K have been observed. The presence of grain boundaries appears to be very detrimental to achieving large magnetoresistance in the lanthanum manganite compounds. The fact th...

358 citations

Journal ArticleDOI
TL;DR: The low-field magnetoresistance properties of polycrystalline La0.67Sr0.33MnO3 and La 0.67CaO33MnsO3 thin films with different grain sizes have been investigated and compared with epitaxial films as discussed by the authors.
Abstract: The low-field magnetoresistance (MR) properties of polycrystalline La0.67Sr0.33MnO3 and La0.67CaO33MnO3 thin films with different grain sizes have been investigated and compared with epitaxial films. MR as high as 15% has been observed in the polycrystalline films at a field of 1500 Oe at low temperatures, whereas the MR of the epitaxial films is less than 0.3% in the same field range. Based on the magnetization dependence of the MR, the current-voltage characteristics, and the temperature dependence of the resistivity, we attribute the low-field MR to spin-dependent scattering of polarized electrons at the grain boundaries which serve as pinning centers for the magnetic domain walls.

344 citations