•Large magnetoresistance observed in La0.2Gd0.5Ba0.3MnO3 compound.•Results analyzed considering disorder induced short range interaction.•Size disorder plays vital role for colossal ...magnetoresistance.
The observation of significantly large magnetoresistance at the liquid nitrogen temperature range in the polycrystalline La0.2Gd0.5Ba0.3MnO3 (LGBMO) compound has been addressed in the present manuscript. The motivation of considering LGBMO sample is the average ‘A’ site ionic radius 〈rA〉 and tolerance factor (t), almost same as that of La0.7Sr0.3MnO3 (LSMO), which is a well studied colossal magnetoresistive material. Magnetoresistance of the LGBMO compound has been compared with the LSMO as well as parent compound La0.7Ba0.3MnO3(LBMO) to show the enhancement of magnetoresistance in LGBMO compound. This observed nature has been elucidated considering the disorder induced short range magnetic interaction due to the enhance size disorder parameter (σ2). Our study revels that, size disorder parameter plays the crucial role for enhancing the colossal magnetoresistance.
•Different magnetic ground state appears in nanocrystalline La0.25Ca0.75MnO3 compound.•Magnetocaloric effect was employed as a powerful tool to study the physical properties.•Surface mediated ...ferromagnetism appears due to particle size reduction.
We have detected size-dependent modifications in magnetic ordering in charge ordered nanoparticles through the study of magnetocaloric effect. Due to prominent surface induced magnetism in nanoparticles, it is very difficult to probe the magnetic ordering in charge ordered antiferromagnetic nanoparticles from direct magnetization study, especially at lower magnetic fields, though at higher magnetic fields the antiferromagnetic/charge ordered transition can be visualized properly. We show that, at comparatively lower magnetic fields, the magnetocaloric effect provides a sensitive way for the detection of such ordering transitions.
Magnetic, specific heat and magnetocaloric studies have been performed on rare earth calcium manganites; Ln0.5Ca0.5MnO3 (Ln=Gd, Dy). The observed isothermal magnetic entropy change is fairly large at ...low temperature in the manganites family, which is attributed to the magnetic precursor effect of rare-earth ions. For Gd0.5Ca0.5MnO3, the isothermal magnetic entropy change (−ΔS) at 4K, obtained for 7T magnetic field, is as high as 22.8J/kgK. On the other hand, −ΔS is 8.5J/kgK for Dy0.5Ca0.5MnO3. The large value of magnetic entropy change at the cryogenic temperature range for these compounds is interesting from application point of view.
•No long range magnetic ordering of Gd0.5Ca0.5MnO3 and Dy0.5Ca0.5MnO3 has been observed in magnetization measurement down to T=2K still these compounds show large magnetocaloric effect.•Specific heat of the compounds in absence of magnetic field increases at low temperature (down to 3K).•Results are analyzed considering magnetic precursor effect of rare earth ions (Gd and Dy ions).
In the present study, we have investigated the detailed magnetic and magnetocaloric properties of the rare-earth-based polycrystalline BiGdO3 compound, synthesized by the solid-state reaction method. ...Detailed magnetic measurements show the absence of long-range magnetic ordering down-to 2 K. Zero-field heat capacity study also supports this result. However, all these magnetic and heat capacity measurements reveal the possibility of having a weak short-range antiferromagnetic correlation in this system below 40 K. Detailed analysis of the magnetic isotherms (using modified Langevin function) and field-dependent magnetic entropy change (using mean-field theory) nicely represent the existence of short-range antiferromagnetic correlation in this system. The prepared material also exhibits a large magnetic entropy change of about 25 J kg−1 K−1 at 2.6 K and a large adiabatic temperature change of 14.8 K at 12 K for the magnetic field change of 0–70 kOe. This observed large magnetocaloric effect at this low temperature region is possibly a consequence of the absence of long-range magnetic ordering and the presence of field-induced ferromagnetic behaviour in this BiGdO3 compound.
•Short-range antiferromagnetic correlation is observed in BiGdO3 compound.•This correlation is nicely established by the modified Langevin function.•BiGdO3 shows a large magnetocaloric effect (MCE) in low temperature region.•Interrelations between MCE and this short-range correlation in BiGdO3 are discussed.
We have carried out an experimental investigation of magneto-transport and magnetic properties of charge-ordered Pr0.67Ca0.33MnO3 (PCMO) and ferromagnetic La0.67Sr0.33MnO3 (LSMO) nanoparticles along ...with a nanocomposite consisting of those two types of nanoparticles. From the magneto-transport measurements, clear irreversibility is observed in the field dependence of resistance due to magnetic field cycling in the case of PCMO nanoparticles. The value of resistance increases during such a field cycling. However such an irreversibility is absent in the case of LSMO nanoparticles as well as nanocomposites. On the other hand, the magnetic measurements indicate the gradual growth of antiferromagnetic phases in all samples leading to a decrease in magnetization. These inconsistencies between magneto-transport and magnetic behaviors are attributed to the magnetic training effects.
•The resistance value in Pr0.67Ca0.33MnO3 nanoparticles is found to increase owing to the magnetic field cycling.•No anomaly in resistance was found in Pr0.67Ca0.33MnO3–La0.67Sr0.33MnO3 nanocomposite.•Magnetic measurements indicate the training effect in nanostructure compounds.
•Large magnetoresistance appeared in the presence of comparatively lower magnetic field in nanocrystalline Nd0.5Ca0.5MnO3 compound.•Observation of the low field magnetoresistance may be important for ...in magnetic field sensor related technology.•Influences of the ferromagnetic phase fraction as well as ferromagnetic interaction in nanocrystalline samples on magnetic and magneto-transport properties were addressed.
Magnetic and magneto-transport properties of nanocrystalline Nd0.5Ca0.5MnO3 compound are presented. In contrast to its bulk counterparts, with modification of the magnetic grounds state, large magnetoresistance appeared in the presence of comparatively lower magnetic field in nanocrystalline compound. Additionally, the magnetic field induced insulator-metal transition took place in nanocrystalline compound with negligible thermal hysteresis. From application perspectives, observation of the low field magnetoresistance in this compound may be important for several uses in magnetic field sensor related technology. Fundamentally, the influences of the ferromagnetic phase fraction as well as the induced ferromagnetic interaction in nanocrystalline samples on magnetic and magneto-transport properties were addressed.
Summary Objectives To review the epidemiology of candidemia in a UK tertiary referral center. Methods Clinical and laboratory data from patients with candidemia were collected prospectively from ...October 1, 2005 to June 30, 2008 (a 33-month period). Results A total of 107 episodes were identified. The incidence was 10.9 episodes/100 000 bed-days. The most common predisposing factors were the use of broad-spectrum antibiotics (92%), the presence of an intravascular device (IVD) (82%), admission to an intensive care unit (ICU) (51%), and recent surgery (50%). Non- Candida albicans species accounted for 58% of the episodes, which is higher than the percentage reported from other UK centers. C. albicans was the most common species, accounting for 43% of episodes, followed by C. glabrata (31%) and C. parapsilosis (20%). Overall C. tropicalis , C. krusei , C. norvegensis , and C. lusitaniae caused 7% of episodes. The crude 30-day mortality rate was 37%. Advanced age ( p = 0.003) and the presence of septic shock ( p = 0.038) were associated with mortality. Conclusions Candidemia continues to be associated with a high mortality. Preventative measures should be targeted against high-risk hospitalized patients, especially those in ICUs, the elderly, and those undergoing major surgery. Local surveillance of candidemia is important to optimize management.
Investigation of the magnetic ground state and magnetocaloric properties of the polycrystalline Pr
0.65
(Ca
0.80
Sr
0.20
)
0.35
MnO
3
compound has been carried out in detail. In addition to the ...charge-orbital ordering and antiferromagnetic ordering transition, a weak ferromagnetic (FM) phase has been recognized from its temperature dependence of magnetization as well as from the change of magnetic entropies. The influence of such ferromagnetic phase on magnetocaloric effect have been examined properly in the presence of different magnetic fields. Moreover, a magnetic phase diagram, derived from the magnetic isotherms and magnetocaloric effect has been constructed to understand evolution of the weak ferromagnetic phase with external magnetic field at low temperature region.
The intermetallic compound Dy
5
Pd
2
has been investigated by means of structural, magnetic, heat capacity, and electrical resistivity measurements. The results indicate the formation of a cluster ...glass state below 42 K, which originates from atomic disorder and spin frustration in the magnetic atom sublattice of the cubic unit cell. The behavior of the heat capacity and electrical resistivity of Dy
5
Pd
2
has also been studied theoretically. The magnetic part of the specific heat exhibits a
T
3/2
temperature dependence below the cluster glass freezing temperature. A minimum in the temperature dependence of the resistivity has been observed around 60 K. This behavior has been interpreted in terms of the combined effects of electron-electron interactions and weak localization as well as contributions from magnetic and phonon scattering.
A resistance minimum in the temperature dependence of Dy
5
Pd
2
has been interpreted in terms of contributions from magnetic and phonon scattering, electron-electron interactions and weak localization.
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