Kirandeep Singh

Strain mediated coupling in magnetron sputtered multiferroic PZT/Ni-Mn-In/Si thin film heterostructure

The strain mediated electrical and magnetic properties were investigated in PZT/Ni-Mn-In heterostructure deposited on Si (100) by dc/rf magnetron sputtering. X-ray diffraction pattern revealed that (220) orientation of Ni-Mn-In facilitate the (110) oriented tertragonal phase growth of PZT layer in PZT/Ni-Mn-In heterostructure. A distinctive peak in dielectric constant versus temperature plots around martensitic phase transformation temperature of Ni-Mn-In showed a strain mediated coupling between Ni-Mn-In and PZT layers. The ferroelectric measurement taken at different temperatures exhibits a well saturated and temperature dependent P-E loops with a highest value of Psat ∼ 55 μC/cm2 obtained during martensite-austenite transition temperature region of Ni-Mn-In. The stress induced by Ni-Mn-In layer on upper PZT film due to structural transformation from martensite to austenite resulted in temperature modulated Tunability of PZT/Ni-Mn-In heterostructure. A tunability of 42% was achieved at 290 K (structural...

Direct and converse magneto-electric coupling in ferromagnetic shape memory alloys based thin film multiferroic heterostructures

The ferromagnetic shape memory driven alterations in strain mediated direct and converse magnetoelectric coupling (DME & CME) was realized in sputtered deposited PZT/Ni-Mn-In multiferroic hetero-junctions. The ferroelectric (P-E loops), dielectric (e vs frequency, e-E), and voltage modulated magnetic anisotropy measurements (M-E curves) were executed in the plane (hard axis) and out of the plane (easy axis) of the functional magnetic material based PZT/Ni-Mn-In bilayer structure. A gain of ∼16 μC/cm2 in maximum polarization (Pmax) and ∼12% in tunability (nr) were observed along an easy magnetic axis of Ni-Mn-In. The butterfly shaped normalized magnetization (M/Ms) vs electric field (applied across the heterostructure) [M-E] plots evident the strain character of CME coupling. The co-action of (i) dissimilar carrier concentration between high symmetric austenitic cubic phase and low symmetry martensite phase of ferromagnetic shape memory alloys and (ii) martensitic transformation induced magnetization chang...

Vertically arrays of Si-LaNiO3/BiFeO3/Au core-shell nano-capacitors for prominent coupled electro-optic effect

The current study delivers the first assessment of well-separated cone shaped n-type epitaxial BiFe0.9Mn0.1O3 (n-BFMO) shells integrated on LaNiO3 (LNO) buffered vertical arrays of p-type nanoporous Si nanowire cores as an absorber for high efficiency and sustainable all- oxide photovoltaic devices. The photovoltaic effect of the LNO/n-BFMO/Au radial heterojunction is investigated by registering the current-voltage curves under AM 1.5 (100 mW cm−2) illumination conditions at various ferroelectric polarization states of BFMO. The as-deposited LNO/BFMO/Au nanowire arrays fabricated by scalable Pulsed Laser deposition are completely self-polarized and produced a remarkably large open circuit photovoltage up to 0.53 V under zero poling condition. The direction of photocurrent and photovoltage is reversibly switchable in response to ferroelectric polarization switching. The short circuit photocurrent “ISC” and open circuit voltage “VOC” depict a hysteresis loop which is more or less identical to that of ferroe...

Four logic states of tunneling magnetoelectroresistance in ferromagnetic shape memory alloy based multiferroic tunnel junctions

This study illustrates the approach to obtain four logic states of ferromagnetic shape memory alloy based multiferroic tunnel junction (MFTJ). In order to achieve giant tunneling electroresistance (TER) and tunneling magnetoresistance (TMR), Ni-Mn-In and Ni-Mn-Sb layers were chosen as electrodes, as well as the concept of the composite barrier was adopted using the STO/PZT [SrTiO3, Strontium Titanate/PbZr0.52Ti0.48O3 (Lead Zirconate Titanate)] (dielectric/ferroelectric) barrier layer. Equated to MFTJ with a single PZT barrier, the introduction of a STO paraelectric (dielectric) barrier is shown to be effective in improving both the TER and TMR of the MFTJs. Particularly, the TER ratio is greatly enhanced by 168% relative TER change: ΔTERTER=TER2−TER1TER1×100. This is described in terms of the increased asymmetry in the electrostatic modulation on the barrier potential profile with respect to the Ferroelectric (FE) polarization direction. We show that due to the coupling between FE polarization and magneti...

Temperature Attuned Charge and Strain Co-mediated Giant Magnetoelectric (M-E) Coupling for Non-volatile Memory Device Applications

The current study explored the investigation of direct strain and charge co-mediated Magnetoelectric (ME) coupling in magnetron sputtered ultra thin PZT /Ni-Mn-In (80 nm/30 nm) multiferroic heterostructure. The evidence of interfacial charges responsible for interaction between FE and FM layers at low thickness regime was manifested from abnormalities of C-V curves from typical butterfly behavior of ferroelectrics, resistance versus voltage plots as well as from magnetodielectric measurements. The signature of strain mediated coupling was evident from the profound variation in maximum polarization (Pmax) with temperature.