Braj Bhusan Singh
@niser.ac.in
INSPIRE Faculty/School of Physical Sciences
National Institute of Science Education and Research (NISER), Bhubaneswar, India, 752050
RESEARCH INTERESTS
spintronics, magnetic tunnel junctions, exchange bias, topological insulators, 2D materials, skyrmions,
Scopus Publications
Scholar Citations
Scholar h-index
Scholar i10-index
Scopus Publications
Abhisek Mishra, Pushpendra Gupta, V. Thiruvengadam, Braj Bhusan Singh, and Subhankar Bedanta
Elsevier BV
Brindaban Ojha, Braj Bhusan Singh, Minaxi Sharma, Sougata Mallick, Vincent Jeudy, André Thiaville, Stanislas Rohart, and Subhankar Bedanta
Springer Science and Business Media LLC
Pushpendra Gupta, Braj Bhusan Singh, Abhisek Mishra, Aditya Kumar, Anirban Sarkar, Markus Waschk, and Subhankar Bedanta
World Scientific Pub Co Pte Ltd
The generation of spin current in materials with high spin–orbit coupling is one of the primary topics for future spintronic applications. In this context, the high conversion efficiency of spin current to charge current is desired. Ferromagnetic resonance (FMR)-based inverse spin Hall effect (ISHE) is a quite popular method to study such spin-to-charge conversion. Here microwave frequency plays a crucial role in generating spin current which further gets converted to charge current due to spin–orbit interaction of the given material. In this work, we show the effect of microwave frequency on spin-to-charge current conversion efficiency in La[Formula: see text]Sr[Formula: see text]MnO3/Pt heterostructure prepared by oxygen-assisted molecular beam epitaxy (OMBE). From the ISHE analysis the maximum spin pumping voltage of ∼98 μV has been observed. Further spin Hall angle has been calculated for different frequencies and the maximum calculated value (∼0.06) for this system has been obtained at 14[Formula: see text]GHz.
Mona Bhukta, Braj Bhusan Singh, Sougata Mallick, Stanislas Rohart, and Subhankar Bedanta
IOP Publishing
Abstract Topological magnetic textures, characterized by integer topological charge S, are potential candidates in future magnetic logic and memory devices, due to their smaller size and expected low threshold current density for their motion. An essential requirement to stabilize them is the Dzyaloshinskii–Moriya interaction (DMI) which promotes a particular chirality, leading to a unique value of S in a given material. However, recently coexistence of skyrmions and antiskyrmions, with opposite topological charge, in frustrated ferromagnets has been predicted using J 1–J 2–J 3 classical Heisenberg model, which opens new perspectives, to use the topological charge as an additional degree of freedom. In this work, we propose another approach of using a synthetic antiferromagnetic system, where one of the ferromagnetic (FM) layer has isotropic and the other FM layer has anisotropic DMI to promote the existence of skyrmions and antiskyrmions, respectively. A frustrated interaction arises due to the coupling between the magnetic textures in the FM layers, which enables the stabilization and coexistence of 6 novel elliptical topological textures.
Shaktiranjan Mohanty, Minaxi Sharma, Ashish Kumar Moharana, Brindaban Ojha, Esita Pandey, Braj Bhusan Singh, and Subhankar Bedanta
Springer Science and Business Media LLC
Braj Bhusan Singh, Koustuv Roy, Pushpendra Gupta, Takeshi Seki, Koki Takanashi, and Subhankar Bedanta
Springer Science and Business Media LLC
AbstractFerromagnetic materials exhibiting low magnetic damping (α) and moderately high-saturation magnetization are required from the viewpoints of generation, transmission, and detection of spin waves. Since spin-to-charge conversion efficiency is another important parameter, high spin mixing conductance $$({g_{r}^{\\uparrow \\downarrow}})$$ ( g r ↑ ↓ ) is the key for efficient spin-to-charge conversion. Full Heusler alloys, e.g., Co2Fe0.4Mn0.6Si (CFMS), which are predicted to be 100% spin-polarized, exhibit low α. However, $$g_r^{ \\uparrow \\downarrow }$$ g r ↑ ↓ at the interface between CFMS and a paramagnet is not fully understood. Here, we report investigations of spin pumping and the inverse spin Hall effect in CFMS/Pt bilayers. Damping analysis indicates the presence of significant spin pumping at the interface of CFMS and Pt, which is also confirmed by the detection of an inverse spin Hall voltage. We show that in CFMS/Pt, $$g_r^{ \\uparrow \\downarrow }$$ g r ↑ ↓ (1.70 × 1020 m−2) and the interface transparency (83%) are higher than the values reported for other ferromagnetic/heavy metal systems. We observed a spin Hall angle of ~0.026 for the CFMS/Pt bilayer system.
Koustuv Roy, Abhisek Mishra, Pushpendra Gupta, Shaktiranjan Mohanty, Braj Bhusan Singh, and Subhankar Bedanta
IOP Publishing
High spin to charge conversion efficiency is a requirement for spintronic devices, which are governed by spin pumping and the inverse spin Hall effect (ISHE). In the last decade, ISHE and spin pumping have been heavily investigated in ferromagnet/heavy metal (HM) heterostructures. Recently, antiferromagnetic (AFM) materials have been found to be a good replacement for HMs because AFMs exhibit terahertz spin dynamics, high spin–orbit coupling, and absence of the stray field. In this context, we have performed the ISHE in CoFeB/IrMn heterostructures. Spin pumping studies are carried out for Co40Fe40B20(12 nm)/Cu(3 nm)/Ir50Mn50(t nm)/AlO x (3 nm) samples where t value varies from 0 to 10 nm. Damping in all the samples is higher than in the single layer CoFeB which indicates that spin pumping due to IrMn is the underneath mechanism. Further, the spin pumping in the samples is confirmed by angle dependent ISHE measurements. We have also disentangled other spin rectifications effects and found that the spin pumping is dominant in all the samples. From the ISHE analysis the real part of spin mixing conductance ( gr↑↓ ) is found to be 0.704 ± 0.003 × 1018 m−2.
Biswajit Sahoo, Koustuv Roy, Pushpendra Gupta, Abhisek Mishra, Biswarup Satpati, Braj Bhusan Singh, and Subhankar Bedanta
Wiley
Large charge-to-spin conversion (spin Hall angle) and spin Hall conductivity are prerequisites for development of next generation power efficient spintronic devices. In this context, heavy metals (e.g. Pt, W etc.), topological insulators, antiferromagnets are usually considered because they exhibit high spin-orbit coupling (SOC). In addition to the above materials, 5d transition metal oxide e.g. Iridium Oxide (IrO 2 ) is a potential candidate which exhibits high SOC strength. Here we report a study of spin pumping and inverse spin Hall effect (ISHE), via ferromagnetic resonance (FMR), in IrO 2 /CoFeB system. We identify the individual contribution of spin pumping and other spin rectification effects in the magnetic layer, by investigating the in-plane angular dependence of ISHE signal. Our analysis shows significant contribution of spin pumping effect to the ISHE signal. We show that polycrystalline IrO 2 thin film exhibits high spin Hall conductivity and spin Hall angle which are comparable to the values of Pt.
Sagarika Nayak, Palash Kumar Manna, Braj Bhusan Singh, and Subhankar Bedanta
Royal Society of Chemistry (RSC)
We have observed the effect of spin glass frustration on exchange bias properties in NiMn (t nm)/CoFeB (5 nm) bilayers.
Manas Kumar Dalai, Braj Bhusan Singh, Salila Kumar Sethy, Satyaprakash Sahoo, and Subhankar Bedanta
Elsevier BV
Au and Ag are known to be metallic and none of them have shown independently superconductivity. Here we show superconductivity in Ag implanted Au thin films. Ag implanted Au films of different thicknesses have been studied using four probe resistance versus temperature measurements. We have also measured the pristine samples (i.e. without any implantation) to compare the transport properties. The superconducting transition occurs around ~2 K (TC) for Ag implanted 20 nm Au film (the lowest resistance observed below TC is ~10-6 Ohm). Change of Tc towards lower temperatures has been observed under the effect of increasing current and magnetic field which endorses the superconducting state. Further the V~I measurements were carried out to verify the superconducting nature. On the other hand, the pristine samples clearly did not exhibit superconductivity down to 1.6 K. Our results open an avenue for further exploring this type of novel superconductivity for future applications.
Pushpendra Gupta, Braj Bhusan Singh, Koustuv Roy, Anirban Sarkar, Markus Waschk, Thomas Brueckel, and Subhankar Bedanta
Royal Society of Chemistry (RSC)
Manganites are an interesting class of materials because they exhibit high spin polarization and low damping. We observed both spin pumping and anti-damping in La0.67Sr0.33MnO3/Pt system which makes it promising for future spintronic applications.
Aroop Kumar Behera, Chandrasekhar Murapaka, Sougata Mallick, Braj Bhusan Singh, and Subhankar Bedanta
IOP Publishing
Skyrmion racetrack memory has a lots of potential in future non-volatile solid state devices. In general such devices require current to nucleate skyrmions via spin transfer torque (STT) effect. Further the current is also required to drive the skyrmions in the nanowire device. However the current applied during nucleation of successive skyrmions may have unwanted perturbation \\emph{viz.} Joule heating and skyrmion Hall effect, on the propagation of previously generated skyrmions. Therefore new methodology is required to decouple the generation and propagation of skyrmions. Here we present a novel route via micromagnetic simulation for generation of skyrmions from triangular antidot structure in a ferromagnetic nanotrack using local oersted field. Antidots are holes in a magnetic nanoelement. Controlled skyrmion injection can be achieved by tuning the dimensions of the antidots that are placed at either end of the nanotrack. Multiple skyrmions can be simultaneously generated by incorporating more number of antidots. Here we propose a novel design to realise skyrmionic racetrcak memory where one can individually generate and manipulate the skyrmions within the nanotrack.
Braj Bhusan Singh, Koustuv Roy, J. Arout Chelvane, and Subhankar Bedanta
American Physical Society (APS)
Noncollinear antiferromagnetic (AFM) materials have drawn research interest because they exhibit large anomalous Hall effect at room temperature (RT) due to large Berry curvature. ${\\mathrm{Mn}}_{3}\\mathrm{Ga}$ is a noncollinear AFM in which the order of Mn magnetic moments is arranged in inverse triangular configuration on a kagome lattice. It makes ${\\mathrm{Mn}}_{3}\\mathrm{Ga}$ a promising candidate for inverse spin Hall effect (ISHE) study which has not been studied before. In this work, investigation of ISHE and spin pumping in polycrystalline ${\\mathrm{Mn}}_{3}\\mathrm{Ga}$/CoFeB heterostructures at RT has been performed. Angle-dependent measurements of ISHE have been performed in order to disentangle various spin-rectification effects. Spin-mixing conductance (${g}_{\\mathrm{eff}}^{\\ensuremath{\\uparrow}\\ensuremath{\\downarrow}})$, spin Hall angle $({\\ensuremath{\\theta}}_{SH})$, and spin Hall conductivity (${\\ensuremath{\\sigma}}_{SH}$) are evaluated to be $(5.0\\ifmmode\\pm\\else\\textpm\\fi{}1.8)\\ifmmode\\times\\else\\texttimes\\fi{}{10}^{18}\\phantom{\\rule{0.16em}{0ex}}{\\mathrm{m}}^{\\ensuremath{-}2}, 0.31\\ifmmode\\pm\\else\\textpm\\fi{}0.01$, and $7.5\\ifmmode\\times\\else\\texttimes\\fi{}{10}^{5}\\phantom{\\rule{0.28em}{0ex}}(\\ensuremath{\\hbar}/2e)\\phantom{\\rule{0.16em}{0ex}}{\\mathrm{\\ensuremath{\\Omega}}}^{\\ensuremath{-}1\\phantom{\\rule{4pt}{0ex}}}\\phantom{\\rule{0.16em}{0ex}}{\\mathrm{m}}^{\\ensuremath{-}1}$, respectively. The observed value of ${\\ensuremath{\\theta}}_{SH}$ is higher than ${\\mathrm{Mn}}_{3}\\mathrm{Sn}$ and comparable to the ${\\mathrm{IrMn}}_{3}$, which is also a noncollinear AFM. Large spin Hall angle makes ${\\mathrm{Mn}}_{3}\\mathrm{Ga}$ a promising candidate for future spintronics devices.
Braj Bhusan Singh, Sukanta Kumar Jena, Manisha Samanta, Kanishka Biswas, and Subhankar Bedanta
American Chemical Society (ACS)
Bi2Se3 is a well-established topological insulator (TI) having spin momentum locked Dirac surface states at room temperature and predicted to exhibit high spin to charge conversion efficiency (SCCE) for spintronics applications. The SCCE in TIs is characterized by an inverse Edelstein effect length (λIREE). We report an λIREE of ∼0.36 nm, which is the highest ever observed in Bi2Se3. Here, we performed spin pumping and inverse spin Hall effect (ISHE) in an electron beam-evaporated Bi2Se3/CoFeB bilayer. The Bi2Se3 thickness dependence of λIREE, perpendicular surface anisotropy (KS), spin mixing conductance, and spin Hall angle confirmed that spin to charge conversion is due to spin momentum locked Dirac surface states. We propose that the role of surface states in SCCE can be understood by the evaluation of KS. The SCCE is found to be high when the value of KS is small.
Sagarika Nayak, Sudhansu Sekhar Das, Braj Bhusan Singh, Timothy R. Charlton, Christy J. Kinane, and Subhankar Bedanta
Royal Society of Chemistry (RSC)
We deposited Fe/NiFe bilayers using magnetron sputtering and studied their static and dynamic properties. We performed PNR measurements and investigated whether the interfacial exchange coupling is responsible for the tuning of the magnetic properties.
Esita Pandey, Braj Bhusan Singh, Purbasha Sharangi, and Subhankar Bedanta
IOP Publishing
The demand of fast and power efficient spintronics devices with flexibility requires additional energy for magnetization manipulation. Stress/and strain have shown their potentials for tuning magnetic properties to the desired level. Here, we report a systematic study for the effect of both tensile and compressive stresses on the magnetic anisotropy (MA). Further the effect of stress on the domain structure and magnetization relaxation mechanism in a perpendicularly magnetized Co/Pt film has been studied. It is observed that a minimal in-plane tensile strain has increased the coercivity of the film by 38$\\%$ of its initial value, while a very small change of coercivity has been found under compressive strain. The size of ferromagnetic domains decreases under tensile strain, while no change is observed under the compressive strain. Magnetization relxation measured at sub-coercive fields yields longer relaxation time in the strained state.
Subhankar Bedanta, J. Arout Chelvane, P. Saravanan, Braj Bhusan Singh, Ajaya K. Nayak, and Wolfgang Kleemann
Springer Science and Business Media LLC
Braj Bhusan Singh and Subhankar Bedanta
American Physical Society (APS)
Antiferromagnetic (AFM) materials recently have shown interest in the research in spintronics due to its zero stray magnetic field, high anisotropy, and spin orbit coupling. In this context, the bi-metallic AFM Mn2Au has drawn attention because it exhibits unique properties and its Neel temperature is very high. Here, we report spin pumping and inverse spin Hall effect investigations in Mn2Au and CoFeB bilayer system using ferromagnetic resonance. We found large spin Hall angle {\\theta}_SH = 0.22
Sagarika Nayak, Palash Kumar Manna, Thiruvengadam Vijayabaskaran, Braj Bhusan Singh, J. Arout Chelvane, and Subhankar Bedanta
Elsevier BV
We have performed magnetic measurements like temperature (T), cooling field (HFC) dependence of exchange bias (EB) and training effect to investigate the magnetic nature of the interface of the Fe/Ir20Mn80 systems. Thin film bilayer samples of different thicknesses of Ir20Mn80 have been prepared by dc magnetron sputtering at room temperature. The variation of exchange bias field (HEB) with the increase in thickness of Ir20Mn80 predicts the antiferromagnet (AFM) bulk spins contribution to EB. Exponential decay of HEB and coercive field (HC) with temperature reveals the presence of spin glass (SG) like interface. Also, the decrease of HEB with increasing HFC confirms the SG like frustration at the interface. Further, the fitting of training effect experimental data envisages the presence of frozen and rotatable spins at the magnetically frustrated interface of these EB systems.
V. Thiruvengadam, B. B. Singh, T. Kojima, K. Takanashi, M. Mizuguchi, and S. Bedanta
AIP Publishing
L10 ordered magnetic alloys such as FePt, FePd, CoPt and FeNi are well known for their large magnetocrystalline anisotropy. Among these, L10-FeNi alloy is economically viable material for magnetic recording media because it does not contain rare earth and noble elements. In this work, L10-FeNi films with three different strengths of anisotropy were fabricated by varying the deposition process in molecular beam epitaxy system. We have investigated the magnetization reversal along with domain imaging via magneto optic Kerr effect based microscope. It is found that in all three samples, the magnetization reversal is happening via domain wall motion. Further ferromagnetic resonance (FMR) spectroscopy was performed to evaluate the damping constant and magnetic anisotropy. It was observed that the FeNi sample with moderate strength of anisotropy exhibits low value of damping constant ~ 4.9X10^-3. In addition to this, it was found that the films possess a mixture of cubic and uniaxial anisotropies.
Sagarika Nayak, Braj Bhusan Singh, Sougata Mallick, and Subhankar Bedanta
IOP Publishing
Braj B. Singh, Sukanta K. Jena, Manisha Samanta, Kanishka Biswas, Biswarup Satpati, and Subhankar Bedanta
Wiley
Aroop Kumar Behera, Swapna Sindhu Mishra, Sougata Mallick, Braj Bhusan Singh, and Subhankar Bedanta
IOP Publishing
We have performed micromagnetic simulations to study the formation of skyrmions from an initial single bubble domain state in ferromagnetic elements with different shapes having perpendicular anisotropy. The strength of Dzyaloshinskii–Moriya interaction (D) and uniaxial anisotropy (K) are varied to elucidate the regime in which skyrmion formation can take place. It is found that for a certain combination of D and K, skyrmion formation does not happen. Further, we also observed that for large D and small K values, finite size effect dominates, which in turn hinders the formation of typical Neel (spherical) skyrmions. However, the resulting magnetic phase is skyrmionic in nature and has different shapes. We also have found that the shape of the magnetic nano element has a significant role in determining the final magnetic state in addition to the competing D and K values.
Sougata Mallick, Srijani Mallik, Braj Bhusan Singh, Niru Chowdhury, Ryszard Gieniusz, Andrzej Maziewski, and Subhankar Bedanta
IOP Publishing
Sagarika Nayak, Sougata Mallick, Braj Bhusan Singh, and Subhankar Bedanta
IOP Publishing