Magnetotransport Properties Of Pr0 Research Articles

Structural, electrical, and magneto-transport properties of Pr0.7Sr0.3MnO3: Al2O3 composites

Incorporation of insulating secondary phase into manganite composites can enhance the low-field magnetoresistance (LFMR). This work reports the structural and electrical transport properties of (1-x) Pr0.7Sr0.3MnO3 (PSMO): x Al2O3 composites synthesised by solid-state reaction method. X-ray diffraction (XRD) patterns indicated that Mn-O-Mn bond distance and angle were disturbed due to the substitution of Al3+ at Mn-site of PSMO system. This subsequently increased the resistivity of composite samples and shifted the metal-insulator transition temperature (TMI) to lower temperatures as increasing content of Al2O3. LFMR effect was observed as the magnetoresistance values increase monotonically with the decreasing temperature.

Structural, magnetic and magneto-transport properties of Pr0.5Ca0.5Mn0.9V0.1O3: Indication of large field coefficient of resistance (FCR)

Structural, magnetic and magneto-transport properties of polycrystalline Pr0.5Ca0.5Mn0.9V0.1O3 have been studied. The incorporation of vanadium attributes to enhancement in the Mn3+/Mn4+ ratio as well as density of conducting eg carriers, which affects the magnetic and electrical behavior of the system. On cooling, a multi-phase separated “paramagnetic (PM) – charge-ordered antiferromagnetic (COAFM) – ferromagnetic (FM) – reentrant spin glass (RSG)” phases are observed with the characteristic charge ordering temperature TCO = 233 K and Neel temperature TN = 143 K. Field-induced first-order magnetic phase transition from a charge-ordered antiferromagnetic state to a ferromagnetic cluster glass state takes place at TC = 44 K. A 7 T magnetic field induces metal–insulator transition at TMI = 163 K. At low temperatures, strong memory-effect and colossal magnetoresistance (CMR) ~ 99.99% are observed in resistivity data. The sample shows a high field coefficient of resistance (FCR) value of about 855% in the low-temperature regime.

Size Effects on Charge Transport Mechanisms and Magnetotransport Properties of Pr0.67Sr0.33MnO3 Nanoparticles

This paper covers a detailed study of the sintering temperature (TS) effect on the electrical and magnetotransport properties of Pr0.67Sr0.33MnO3 nanoparticles prepared by sol–gel method. The temperature dependence of resistivity displays a metal–insulator transition with increasing temperature. The electrical resistivity is strongly affected by particle size. The resistivity minimum at low temperature is associated to electron–electron coulombic interactions. Magnetotransport analysis was carried out using a phenomenological percolation model for all our samples. The obtained results indicate that a percolation model is not suitable for samples presenting high magnetic disorder. The magnetoresistance (MR) can be modulated by particle size effect. We have recorded considerable MR values (−MR(T) = 34% at 10 K for a 1T field when TS = 850°C, −MR(T) = 33% at 290 K for a 2T field when TS = 1000°C and −MR(H) = 33% at 5 K for a 1T field when TS = 700°C). The considerable MR values indicate the possibility of using these samples for several technological applications.

Magnetic phase separation in polycrystalline Pr0.5−xBixSr0.5MnO3 (x ≤ 0.15)

In this paper, magnetic phase coexistence and magnetotransport properties of Pr0.5–xBixSr0.5MnO3 (x ≤ 0.15) samples have been studied. Our specimens demonstrate complicated magnetic properties through the presence of several transitions as a function of temperature. With increase in bismuth content, a spin–glass–like–state appears at low temperatures and long–range charge ordering can be observed for x = 0.15. Magnetization and resistivity seems to be sensitive to magnetic field cycling, testifying the presence of training effect. Both, magnetic phase separation phenomenon and 6s2 lone pair electrons of Bi3+ ions, play a key role in the governance of the physical response of studied specimens.

Tuning the magnetic and magnetotransport properties of Pr0.8Sr0.2MnO3 manganites through Bi-doping

Magnetic and magneto-transport properties of Pr0.8−xBixSr0.2MnO3 (x = 0, 0.05 and 0.1) compounds were investigated. All samples exhibited a second-order paramagnetic-ferromagnetic transition with the decrease in temperature. The Curie temperature decreased from 210 to 140 K with the Bi-doping content. The electrical resistivity of the parent sample was described by the phenomenological percolation model, which is based on the phase segregation. The metallic character observed in the pristine sample was reduced, and then entirely suppressed by 10% of Bi. The resistivity data for doped samples were described using Mott’s variable range hopping model at high temperatures and by electron-electron interaction and inelastic scattering mechanisms at low temperatures. A Colossal magnetoresistance (MR) was observed in the studied samples. The parent sample illustrated the predominance of intrinsic MR but in doped compounds, MR curves revealed the coexistence of intrinsic and extrinsic contributions. Bi-doping was found to enhance the extrinsic MR in Pr0.8−xBixSr0.2MnO3 (0 ≤ x ≤ 0.1) samples.

The effect of post-annealing on the structure and magnetotransport properties of Pr0.5Sr0.5MnO3 thin film

Pr0.5Sr0.5MnO3 (PSMO) thin film is epitaxially grown on (001)-oriented LaAlO3 single-crystal substrate using pulsed laser deposition (PLD). It is found that the as-grown PSMO film shows compressive strain in plane and tensile strain out of the plane. Upon annealing at 900°C in the air, the strain is significantly relaxed. The paramagnetic to ferromagnetic phase transition temperature TC shifts from 200 K to 220 K, and the antiferromagnetic insulating phase is suppressed in the phase separated state at low temperature. In addition, the magnetoresistance (MR) is found to increase around the ferromagnetic transition temperature, whereas it decreases from 99% to 60% at low temperature of 20 K.

A-site-deficiency-dependent structural, magnetic and magnetoresistance properties in the Pr0.6Sr0.4MnO3 manganites

Structural, magnetic and magneto-transport properties of Pr0.6Sr0.4MnO3, Pr0.6Sr0.3□0.1MnO3 and Pr0.5□0.1Sr0.4MnO3 perovskite manganite oxides have been investigated. X-ray diffraction (XRD) analysis using Rietveld refinement has shown that all the samples under investigation crystallize in the orthorhombic structure with Pbnm space group. Strontium vacancy leads to an increase in the unit cell volume. Paramagnetic (PM) to ferromagnetic (FM) transitions have been observed in all the synthesized samples. The Curie temperature was found to be 251K for the strontium-deficient sample, 273K for the stoichiometric sample and 275K for the praseodymium-deficient one. With the decrease in temperature, the two deficient samples exhibit semiconducting–metallic transitions. The resistivity decreases while Tρ increases with the change in the magnetic applied field from 0T to 5T. The strontium-vacancy sample has been proven to exhibit a magnetoresistance value of about 50% at 266K at a magnetic applied field of 5T and seems to be constant below 236K. The praseodymium-deficient one is manifested in another form of MR which increases with the decrease in temperature. This is a clear indication of the low field magnétoresistance (LFMR) behavior.

Structure, ferromagnetism and magnetotransport properties of nanopowders of Pr0.67Ca0.33FexMn1−xO3 manganites oxide prepared by sol–gel method

Structural, magnetic and magneto transport properties of Pr0.67Ca0.33FexMn1−xO3 with 0⩽x⩽0.3 nanopowder samples have been investigated. Powder samples have been elaborated by sol–gel method. Rietveld analysis of powder X-ray diffraction show that the samples crystallise in the orthorhombic perovskite system with Pnma space group. The average crystallite size of 50nm was obtained by X-ray diffraction. The investigated samples exhibit a ferromagnetic to paramagnetic transition with increasing temperature. The presence of manganese in the structure leads to an increase of the Curie temperature as well as to spontaneous magnetization. Electrical investigations showed that all our samples exhibit a semi-conducting behavior at high temperature and a metallic-like one at low temperature. A large magnetoresistance has been observed in the samples studied. The magnetization versus applied magnetic field shows a small coercive field and an unsaturated magnetization which indicates that the nanoparticles of all samples are superparamagnetic at around room temperature.

Magnetotransport properties of Pr0.5Ca0.5MnO3 thin films grown by a solution route

Thin films of Pr0.5Ca0.5MnO3 were fabricated on (001) oriented SrLaAlO4, NdGaO3, and SrTiO3 substrates using a hybrid solution route and spin coating techniques. Good crystalline and epitaxial quality of the films was confirmed with X-ray diffraction and transmission electron microscopy studies. Strain in the film grown on NdGaO3 substrate did not relax during annealing process and the film exhibited charge-ordered insulator phase at low temperatures even with magnetic fields up to 9 T. However, the films on SrLaAlO4 and SrTiO3 substrates (with partially relaxed compressive and tensile strain, respectively) displayed melting of the charge-ordered phase with applied magnetic fields of less than 5 T. The results suggest that strain-relaxation rather than only the type of strain plays an important role in lowering critical melting magnetic fields in these films.

Magnetic phases in Pr0.5Sr0.5Mn1 − x Co x O3 (x ≤ 0.5) solid solutions

The magnetic and magnetotransport properties of Pr0.5Sr0.5Mn1 − xCoxO3 (x ≤ 0.5) solid solutions have been investigated using neutron diffraction methods. The magnetization and electrical conductivity have been measured in magnetic fields up to 140 kOe. It has been established that, during cooling in the temperature range from 160 to 110 K, the compounds of compositions with a cobalt content x ≤ 0.07 undergo a structural phase transition from the high-temperature ferromagnetic phase to the antiferromagnetic phase. A further substitution of cobalt for manganese leads to a stabilization of the inhomogeneous dielectric ferromagnetic state, whereas a state of the cluster spin-glass type has been revealed in compositions with x = 0.15 and 0.20. At x ≥ 0.25, a new magnetic phase with a Curie temperature up to 210 K is formed as a result of the magnetic interaction between manganese and cobalt ions. A magnetic phase diagram of the system under investigation has been constructed.

Phase transformations and magnetotransport properties of the Pr0.5Sr0.5Co1 − x Mn x O3 system

The structural, magnetic, and magnetotransport properties of Pr0.5Sr0.5Co1 − x Mn x O3 (x 0.5, it is described by orthorhombic space group Imma. When the temperature decreases, a structural transformation without changing the symmetry takes place in all compounds. This transformation is caused by an active role of the inner shells of the praseodymium ion in chemical bond formation. The substitution of manganese for cobalt breaks a long-range ferromagnetic order near x ≈ 0.25, and a metal-dielectric transition occurs at x ≈ 0.15. The negative magnetoresistance is found to be maximal near a critical manganese concentration, where a long-range magnetic order is broken; it reaches 95% in a field of 14 T at T = 10 K for x = 0.2. An unusual dielectric magnetic state with a small spontaneous magnetic moment and a sharp transition into a paramagnetic state at T > 200 K is revealed in the concentration range 0.30 ≤ x ≤ 0.65 in spite of the absence of coherent magnetic neutron scattering. A model is proposed to explain the behavior of the magnetic properties in this phase.

Magnetoresistance in the paramagnetic insulating state of Pr0.50Ca0.50CoO3

We have studied the magnetic and magnetotransport properties of Pr0.50Ca0.50CoO3 (prepared using high pressure routes). We find that below the metal-insulator and spin state transition (MIT), the system can be described as a paramagnetic insulator. In this regime, it presents a considerable negative magnetoresistance (20%-40%), while above MIT the magnetoresistance is negligible or even slightly positive. These results seem in contradiction with the spin state picture usually drawn for this system.

Magnetic and Transport Properties of Ni Doped Pr0.5Ca0.5Mn1-xNixO3-δ

ABSTRACTStructural, magnetic and transport properties of Pr0.5Ca0.5Mn1-xNixO3 (x =0, 0.04, 0.07, 0.1) series have been investigated. The substitution of Mn ions by Ni induces drastic changes in the magneto-transport properties of Pr0.5Ca0.5MnO3. The physical behavior depends drastically on O stoichiometry. For the low Ni doping x=0.04, 0.07, spin glass configuration is rather favored than ferromagnetism; while for x=0.10, the ferromagnetic phase is significantly suppressed. Pronounced irreversibility between zero-field cooled (ZFC) and field cooled (FC) magnetization and a kink in the ZFC curve observed for x=0.04 and 0.07 are indicative of spin-glass-like state. Applied hydrostatic pressure of about 10 kbar reduces the temperature of charge ordering in an x=0 sample by about 10 K indicating a pressure induced suppression of the Jahn-Teller distortions and of the electron-phonon coupling. Electron magnetic resonance (EMR) unambiguously evidences appearance of FM phase in Ni doped manganites. Temperature dependence of EMR spectra parameters allow us to speculate on the effect of magnetic inhomogeneities.

Role of A-site deficiency in the magneto-transport properties of Pr0.7Sr0.3MnO3 relaxed films

The magneto-transport properties of thick relaxed A-site deficient films having the composition Pr $_{0.6}\square_{0.1}$ Sr0.3MnO3 (P□SMO with the □ symbol for the Pr vacancy) and Pr0.7Sr $_{0.2}\square_{0.1}$ MnO3 (PS□MO) are studied. A direct comparison with a Pr0.7Sr0.3MnO3 (PSMO)completely relaxed film, deposited under the same growth conditions, shows a reduction of the in-plane parameter a100 associated to an enhancement of the out-plane parameter. The strains (bulk strain eB and biaxial Jahn-Teller strain eJ-T) do vary with the nature of the cationic vacancy. For example, an enhancement of eB of 9% in the PS□MO film (Sr deficient) produces a decrease of TC of 30 K, whereas the Pr deficient P□SMO film exhibits a large reduction of both eB (-16%) and eJ-T (divided by a factor of 5), which enhances TC of 12 K, similarly to previous observations on bulk ceramics. With a reduced resistivity (ρ<0.02 Ω cm), the obtained Pr-deficient film, P□SMO, exhibits the best magneto-transport properties with a decreasing magnetoresistance sensitivity at low field.

Role of strain in magnetotransport properties of Pr0.67Sr0.33MnO3 thin films

We have studied the strain effects on the structural and magnetotransport properties of Pr0.67Sr0.33MnO3 (PSMO) thin films. The PSMO films were epitaxially grown on LaAlO3 (001), SrTiO3 (001), and NdGaO3 (110) substrates that induce biaxial compressive, tensile, and almost no strain in the films, respectively. The film thickness t, varied between 4–400 nm, was used as another controlling parameter of strain for each type of film. There exist two distinct thickness ranges with different thickness dependence of the magnetotransport properties. For t&amp;lt;20 nm, the zero-field resistance peak temperature (Tp) and the high-field magnetoresistance (HFMR) properties are critically dependent on the thickness and the substrate. For t&amp;gt;20 nm, the Tp and the HFMR ratio show weak t dependence. The results show evidence for the effects of the Jahn–Teller type distortion as well as disorders on the resistive transition temperature and the HFMR.