P. S. Solanki

Improvement in resistive switching of Ba-doped BiFeO3 films

We investigate the resistive switching behavior of Ba-doped BiFeO3 (BBFO) films grown on single crystalline SrTi0.99Nb0.01O3 substrates. Observation of diode like I-V behavior and reduction in VC with Ba-content in BBFO films have been understood in the context of modifications in its energy band diagram. Also, I-V curves exhibit hysteresis which has been explained on the basis of migration and recombination of oxygen vacancies under field conditions. Furthermore, increment in Ba-content improves the retention property and ON/OFF switching ratio in BFO films which makes them suitable for applications in switching devices.

Size-controlled electrical properties of sol–gel-grown nanostructured Gd0.95Ca0.05MnO3

In this communication, we report the results of the studies on electrical properties of cost-effective modified sol–gel-grown nanostructured Gd0.95Ca0.05MnO3 (GCMO) manganites sintered at different temperatures. Structural investigations, carried out using X-ray diffraction measurements, reveal the single-phasic nature of GCMO samples having orthorhombic unit cell structure. Frequency-dependent variation in AC conductivity (σAC) has been discussed on the basis of correlated barrier hopping (CBH) mechanism for the GCMO samples sintered at lower temperatures. Sintering temperature-induced transition from CBH mechanism to Maxwell–Wagner relaxation processes has been discussed in detail. Size-induced modifications in the impedance response of the samples have been understood, in detail, using size effects and Cole–Cole plots.Graphical Abstract

STRUCTURAL, TRANSPORT AND MAGNETOTRANSPORT IN NONMAGNETIC Al3+ DOPED MIXED VALENT La0.7Ca0.3Mn1-XAlXO3 MANGANITES

We report the modifications in the transport and magnetotransport in La0.7Ca0.3Mn1-xAlxO3 (LCMAO); x = 0.0, 0.02, 0.04, 0.06, 0.08 and 0.1 polycrystalline manganites synthesized by conventional ceramic method. XRD studies reveal the single phasic orthorhombic structure for all the Al-doped LCMO samples without any detectable impurities and structural phase transition. SEM micrographs show island-like grain growth in all the samples studied. Transport measurements indicate an increase in resistivity and decrease in metal-insulator (M-I) transition temperature (TP) with the increase in Al-concentration. Field and temperature dependent variation in MR for all the Al (x) doped LCMO samples has been discussed in detail in the light of substitution induced structural disorder.

Electroresistance and field effect studies on manganite based heterostructure

Electronic properties of manganites are significantly important for various spintronic applications such as microelectronics, magnetic data storage, communication technologies, and memory devices. Influence of applied electric field on the room temperature charge transport in ZnO/La0.7Sr0.3MnO3/SrNb0.002Ti0.998O3 (SNTO) heterostructure has been investigated using field effect studies. Large negative and positive electroresistance has been observed in heterostructure under various possible circuit geometries. Field effect studies have been carried out using three different circuit geometries, namely: (i) ZnO as a control electrode (ELZ), (ii) SNTO as a control electrode (ELS), and (iii) shorted ZnO and SNTO as control electrodes (ELZS). For this, channel electric field (ECH) dependent variation in channel resistance (RC) (of manganite channel) and I-V (across manganite channel) under various control fields (EC) have been studied. Variation in barrier height (ΦB) with control field (EC) for different geomet...

Temperature-dependent I–V and C–V characteristics of chemically-grown Y0.95Ca0.05MnO3/Si thin films

In this communication, we report the results of the studies on temperature-dependent current—voltage (I–V) and capacitance—voltage (C–V) characteristics of chemical solution deposition-grown Y0.95Ca0.05MnO3/Si films and annealing temperature-induced modified interface dependence on device characteristics. X-ray diffraction results reveal the single phasic nature of films having polycrystalline growth on single crystalline (100) Si substrate. The magnetic nature of the films is confirmed from magnetic force microscopy studies. I–V and C–V characteristics show a strong dependence on the temperature and nature of the film—substrate interface, which has been understood on the basis of the annealing effect involved. Various models and theories have been used to understand the mechanism responsible for the transport across the film—substrate interface. A large rectifying ratio of ~1.2 × 104 has been obtained across the interface annealed at a lower temperature, which becomes almost double in the film annealed at a higher temperature. A large electroresistance of ~600% has been achieved for the interface annealed at a lower temperature. The temperature dependence of C–V behavior recorded across the interfaces of the films is discussed in detail on the basis of free and trapped charge carrier density and interface modifications.

Role of defects in BiFeO3 multiferroic films and their local electronic structure by x-ray absorption spectroscopy

Present study reports the role of defects in the electrical transport in BiFeO3 (BFO) multiferroic films and its local electronic structure investigated by near-edge X-ray absorption fine structure. Defects created by high energy 200 MeV Ag+15 ion irradiation with a fluence of ∼5 × 1011 ions/cm2 results in the increase in structural strain and reduction in the mobility of charge carriers and enhancement in resistive (I-V) and polarization (P-E) switching behaviour. At higher fluence of ∼5 × 1012 ions/cm2, there is a release in the structural strain due to local annealing effect, resulting in an increase in the mobility of charge carriers, which are released from oxygen vacancies and hence suppression in resistive and polarization switching. Near-edge X-ray absorption fine structure studies at Fe L3, 2- and O K-edges show a significant change in the spectral features suggesting the modifications in the local electronic structure responsible for changes in the intrinsic magnetic moment and electrical transp...

Dielectric behavior of nanostructured Y0.95Ca0.05MnO3: Role of sintering temperature

Nanostructured Y0.95Ca0.05MnO3 (YCMO) samples have been synthesized using cost effective sol-gel method. The samples were sintered at various temperatures ranging between 700 – 1100°C (ST). XRD studies reveal the single phasic nature of the samples. Frequency dependent dielectric (e) and modulus (M) behaviors of YCMO samples imply the increase in e and activation energy (Ea) with ST which has been discussed in the light of oxygen vacancies and grain morphology.

Dielectric and Magnetic Behavior of Sol‐Gel Grown BiFeO3 Multiferroic

We report the dielectric and magnetic properties of BiFeO3 (BFO) multiferroic synthesized by modified sol‐gel route. Frequency dependent dielectric constant and loss studies show higher value at lower frequencies while temperature dependent dielectric behaviour show higher value of dielectric constant above 250 K. Low magnetization value is exhibited by the BFO sample studied. DTA study shows the phase transition at 340° C and 816° C.

Role of strain and nanoscale defects in modifying the multiferroicity in nanostructured BiFeO3 films

BiFeO3 (BFO) multifunctional oxide exhibits fascinating multiferroic properties suitable for potential application in nanoscale electronic devices such as non-volatile random accesses memory (FeRAM), field effect transistors, capacitors, logic circuits, etc. In this communication, we report the results of studies on 200 MeV Ag+15 ion irradiation-induced modifications in the structural, microstructural, electrical (I–V, C–V and P–E) and magnetic properties of pulsed laser deposited nanostructured BFO films grown on conducting SrTi0.998O0.002TiO3 (SNTO) substrates. Role of nanoscale structural defects and oxygen vacancies in modifying the physical properties of BFO/SNTO has been discussed in this work.

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.