Priyanka Trivedi

Swift Heavy Ion Irradiation Studies on the Transport in La0.8-xPr0.2SrxMnO3 Manganite Films

Thin films of La0.8-xPr0.2SrxMnO3 (LPSMO) (x = 0.1, 0.2, 0.3) manganite, synthesized using pulsed laser deposition (PLD) technique, were irradiated by 200MeV Ag+15 ions with an ion fluence of 5 × 1011 ions/cm2. Structural and microstructural characterizations have been carried out using XRD and AFM show single crystalline nature of the films having island like grain growth. The structural and grain morphology modifications due to irradiation has been observed. Temperature dependent resistivity measurements have been carried out for all the films before and after irradiation, which reveal a reduction in the resistivity and enhancement in insulator - metal (I-M) transition temperature (TP) with Sr content (x) resulting in improved transport (reduced resistivity and enhanced TP) in the films which can be attributed to the irradiation induced improved crystallinity and grain morphology. Temperature coefficient of resistance (TCR) improves on irradiation which is useful for practical applications.

Studies on the structure and dielectric properties of Ca-doped BiFeO3 multiferroics

ABSTRACT We present the results of studies on the dielectric properties of polycrystalline Bi1-xCaxFeO3 (x = 0.05, 0.10, 0.20) (BCFO) multiferroics. Rietveld refined XRD patterns confirm the single phasic nature of 5% & 10% Ca – doped samples crystallizing in superimposed R3c (Rhombohedral) + Pm 3m (Cubic) space group symmetry while 20% Ca – doped sample crystallize in Pm 3m symmetry. Frequency and temperature dependent dielectric constant (ϵ) studies show the contribution of grain and grain boundaries in the system. Complex impedance graph exhibits a single semicircular arc for all the samples, indicating the contribution of grain interior (bulk) property of the material.

Grain morphology dependent dielectric behaviour of ZnO – BaTiO3 composites

We report the effect of BaTiO3 (BTO) addition in ZnO on the dielectric behaviour of ZnO-BaTiO3 composite in the form of (1-x)ZnO–(x)BTO (x=0.2,0.3,0.4,0.5). Modifications in the structural and microstructural properties of the composite under study have been attributed to the addition of ferroelectric BTO in the host insulating ZnO matrix. Improvement in the overall dielectric performance of ZnO-BTO composite has been observed due to the increase in the dielectric constant and suppression of the dielectric loss. Study of dielectric behaviour of ZnO-BTO composite show that increasing in BTO concentration in ZnO matrix results in the grain boundary modifications and enhancement in relaxor behaviour which has been understood on the basis of percolation phenomena, wherein, BTO modifies the dipole arrangements leading to higher dielectric constant.

Structure & magnetic behavior of Cu doped NdMnO3 manganite

Structural and magnetic properties of pure and Cu doped NdMnO3 manganites have been investigated using room temperature neutron diffraction and temperature dependent magnetization measurements. The partial replacement of Mn3+ by Cu2+ results in the modification in the magnetic behavior of NdMnO3 at low temperature. Temperature dependent magnetization measurements show an onset of magnetic ordering at T ∼ 80 K in pure NdMnO3 and at T ∼ 77 K in NdMn0.95Cu0.05O3. Field dependent magnetization behaviour reveals metamagnetic behaviour for both the samples below 25 K, which becomes considerably weak in NdMn0.95Cu0.05O3 sample at T = 5 K.Structural and magnetic properties of pure and Cu doped NdMnO3 manganites have been investigated using room temperature neutron diffraction and temperature dependent magnetization measurements. The partial replacement of Mn3+ by Cu2+ results in the modification in the magnetic behavior of NdMnO3 at low temperature. Temperature dependent magnetization measurements show an onset of magnetic ordering at T ∼ 80 K in pure NdMnO3 and at T ∼ 77 K in NdMn0.95Cu0.05O3. Field dependent magnetization behaviour reveals metamagnetic behaviour for both the samples below 25 K, which becomes considerably weak in NdMn0.95Cu0.05O3 sample at T = 5 K.

Magnetic structure and magnetism of divalent Zn doped NdMnO3

Structural and magnetic properties of pure and Zn doped NdMnO3 manganites have been investigated using neutron diffraction and ac susceptibility measurements. The partial replacement of Mn3+ by Zn results in the modification in the magnetic behavior of NdMnO3 at low temperature. Temperature dependent ac susceptibility measurements show a broad hump like behavior around ∼ 60 K suggesting the presence of antiferromagnetic ordering. Temperature dependent ND studies on NdMn0.95Zn0.05O3 sample revealed the evolution of antiferromagnetic order around ∼ 75 K, evident from the emergence of (010) Bragg reflection. The intensities of (101) and (111) Bragg peaks in ND patterns increases below 75K which has been attributed to the presence of ferromagnetic (FM) component, getting enhanced at low temperature. Results of the temperature dependent ND and ac susceptibility measurements on NdMn0.95Zn0.05O3 have been discussed in detail.

Resistive switching and magnetic behavior of Bi0.8Ba0.2FeO3 / SrRuO3 / SrTiO3 films: role of thickness-dependent strain

The thickness-dependent resistive switching and magnetic behavior of Bi0.8Ba0.2FeO3/SRO/STO (1 0 0) films have been studied in the context of strain modifications introduced by varying the film thickness. Generation of misfit dislocation results in strain relaxation with an increase in film thickness. All films (50, 100 and 200 nm) show hysteresis in I–V behavior at room temperature with applied voltage V max = ±5 V. Fitting of I–V data suggests that trap-controlled SCLC governs the conduction in HRS in the 50 nm film while in the 100 nm and 200 nm films, the charge transport mechanism is ohmic-type throughout the applied field. The ON/OFF switching ratio and current retention performance decrease with an increase in film thickness, suggesting that substrate-induced strain and interface modifications play an important role in governing the resistive switching mechanism in Bi0.8Ba0.2FeO3 films. A film with lower thickness ~50 nm is found to exhibit the highest magnetization which may be attributed to the increase in oxygen vacancies and compressive strain.