Article
Chemistry, Physical
Xiaoyan Zhu, Yang Li, Yali Xie, Qian Qiu, Cuimei Cao, Xiao Hu, Wenhui Xie, Tian Shang, Yang Xu, Lin Sun, Wenjuan Cheng, Dongmei Jiang, Qingfeng Zhan
Summary: We quantitatively investigated the magnetocrystalline anisotropy of metamagnetic FeRh films epitaxially grown on MgO(001) substrates. We observed that the in-plane fourfold magnetic anisotropy of epitaxial FeRh films is reoriented and enhanced when FeRh undergoes a phase transition from ferromagnetic to antiferromagnetic states. The observed anisotropy is attributed to the exchange coupling between the residual ferromagnetic moments caused by antisite defects and the antiferromagnetic matrix. Furthermore, our first-principles calculations suggest that the lattice compressive strain imposed by the MgO substrate is crucial in determining the magnetic structure of FeRh films.
JOURNAL OF ALLOYS AND COMPOUNDS
(2022)
Article
Chemistry, Physical
Francesco Presel, Christian S. Kern, Thomas G. Bone, Florian Schwarz, Peter Puschnig, Michael G. Ramsey, Martin Sterrer
Summary: The adsorption structure, charge state, and metalation state of porphin on ultrathin Ag(001)-supported MgO(001) films were experimentally determined. The study revealed that the porphin molecules self-metalate at room temperature, forming the corresponding Mg-porphin, regardless of their charge state. Unlike tetraphenyl porphyrin, the self-metalation of porphin occurs even without a negative charge.
PHYSICAL CHEMISTRY CHEMICAL PHYSICS
(2022)
Article
Physics, Condensed Matter
M. De Santis, V Langlais, K. Schneider, X. Torrelles
Summary: MgO ultrathin films are crucial for electronics, spintronics, catalysis, and 2D electronics, with their morphology and interface structure playing a key role in electronic transfer. Research has shown that under specific conditions, a high-quality MgO bilayer can be formed.
JOURNAL OF PHYSICS-CONDENSED MATTER
(2021)
Article
Chemistry, Physical
V Golub, I. R. Aseguinolaza, O. Salyuk, D. Popadiuk, I Sharay, R. Fernandez, V Alexandrakis, S. A. Bunyaev, G. N. Kakazei, J. M. Barandiaran, V. A. Chernenko
Summary: The influence of film thickness on the formation of twinning structure, martensitic transformation, and magnetoelastic properties of epitaxial films of Ni(Co)MnSn magnetic shape memory alloy was investigated. It was found that constraints from the film/substrate interface block the martensitic transformation in the 20 nm thick film, but become possible starting from 50 nm. The formation of a submicron wide, stripe like, periodic structure of twins, controlled by the elastic energy balance between the film/substrate interface and the twin boundaries, is of interest for spintronic or magnonic applications.
JOURNAL OF ALLOYS AND COMPOUNDS
(2021)
Article
Chemistry, Physical
Adam Dziwoki, Bohdana Blyzniuk, Kinga Freindl, Ewa Madej, Ewa Mlynczak, Dorota Wilgocka-Slezak, Jozef Korecki, Nika Spiridis
Summary: Molecular beam epitaxy is enhanced by the presence of an external magnetic field, which impacts the growth morphology and magnetic properties of epitaxial magnetite films on MgO(111). In situ and ex situ characterization techniques revealed that the in-plane magnetic field during deposition influenced the film growth and magnetization process, attributed to modification of the effective magnetic anisotropy. This novel approach expands the capabilities of molecular beam epitaxy for engineering low-dimensional materials.
Article
Materials Science, Multidisciplinary
Bo Yang, Ivan Soldatov, Fenghua Chen, Yudong Zhang, Zongbin Li, Haile Yan, Rudolf Schaefer, Dunhui Wang, Claude Esling, Xiang Zhao, Liang Zuo
Summary: In this study, the magnetic domain and microstructure evolution of epitaxial Ni-Mn-Ga thin films were investigated using wide-field magneto-optical Kerr microscopy. The results showed that the abrupt magnetization changes in the hysteresis loops should be attributed to the magnetic domain evolution.
JOURNAL OF MATERIALS SCIENCE & TECHNOLOGY
(2022)
Article
Materials Science, Multidisciplinary
Shao-Dong Cheng, Lu Lu, Lvkang Shen, Hong-Mei Jing, Ming Liu, Shao-Bo Mi
Summary: The study on the effect of post-annealing on CoFe2O4:MgO nanocomposite films revealed that post-annealing can influence the microstructure and magnetic properties of the nanocomposite films, leading to changes in the distribution of Co and the epitaxial strain state, as well as affecting the in-plane and out-of-plane saturation magnetization and coercivity.
Article
Physics, Applied
Xiao-bin Guo, Xiao-ling Lu, Feng-chao Su, Wen-hai Qiu, Zheng Su, Jia-feng Xie
Summary: This study investigates the correlation between the structure and magnetic properties of FeSi films deposited at different substrate temperatures. The results demonstrate the possibility of preparing soft films with deterministic magnetic anisotropy for practical applications.
JOURNAL OF PHYSICS D-APPLIED PHYSICS
(2022)
Article
Chemistry, Physical
Peijiao Fang, Baiwei Wang, C. P. Mulligan, T. M. Murray, S. Khare, Daniel Gall
Summary: In this study, tungsten carbide films were sputter-deposited onto Mg0(001) substrates at 400 degrees C in Ar - CH4 gas mixtures. The films were found to contain amorphous carbon and carbon vacancies. The epitaxial relationship between the cubic WCy phase layers and the substrate was demonstrated through X-ray diffraction and transmission electron microscopy analyses.
JOURNAL OF ALLOYS AND COMPOUNDS
(2021)
Article
Chemistry, Physical
Wenxuan Zhang, Xutao Wang, Ningning Liu, Jinyue Wang, Yueqiao Qu, Shiyong Wang, Hao Zheng, Yao-Yi Li, Canhua Liu, Jin-Feng Jia
Summary: Using scanning tunneling microscopy and spectroscopy, the molecular arrangement and electronic structure of C60 ultrathin films grown on a SrTiO3(0 0 1) surface were investigated. The monolayer C60 exhibited a short-range ordered molecular arrangement with disordered molecular orientation and a substantially large HOMO-LUMO gap (-4.1 eV). In contrast, C60 in the 2nd and 3rd layers self-assembled into hexagon lattices with a quasi-(2 x 2) superstructure, resulting in a chiral pinwheel structure.
APPLIED SURFACE SCIENCE
(2023)
Article
Chemistry, Physical
Kevin Ruwisch, Tobias Pohlmann, Florian Bertram, Christoph Schlueter, Andrei Gloskovskii, Karsten Kuepper, Joachim Wollschlaeger
Summary: In this work, we conducted a comprehensive study on real-time monitoring of the growth of epitaxial CoxFe3-xO4 thin films. Through time resolved operando HAXPES technique, we observed different growth characteristics under different oxygen partial pressures, including metallic, light oxidic, and cobalt ferrite-like growth.
Article
Materials Science, Multidisciplinary
Hardeep Kumar, Sergio L. Morelhao, Gerson Pessotto, Hardepinder Singh, Anil K. Sinha, Daniel R. Cornejo
Summary: The effect of substrate orientation on the structural and magnetic properties of FeRh thin films is studied. FeRh films with different orientations are obtained on MgO substrates. It is found that lattice strain can tune the temperature of the antiferromagnetic-ferromagnetic phase transition, and a larger thermal hysteresis is observed.
JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS
(2022)
Article
Physics, Applied
T. Kawagoe, S. Suga
Summary: The growth of thin Pd films on Au(001) surfaces has been investigated. The films were found to grow epitaxially with noticeable lattice expansion on the Au(001) surface, and annealing improves the surface morphology. This three-step method enables quasi-layer-by-layer growth.
JOURNAL OF APPLIED PHYSICS
(2022)
Article
Chemistry, Physical
Jannis Thien, Jascha Bahlmann, Andreas Alexander, Kevin Ruwisch, Jari Rodewald, Tobias Pohlmann, Martin Hoppe, Fatih Alarslan, Martin Steinhart, Baki Altuncevahir, Padraic Shafer, Carola Meyer, Florian Bertram, Joachim Wollschlaeger, Karsten Kuepper
Summary: This study presents the magnetic properties and cation ordering of ultrathin Co-rich cobalt ferrite films. The electronic structure and distribution of cations in the films were examined using various characterization techniques. The results show a partially inverse spinel structure and an increased amount of Co3+ cations in the low-spin state for one of the films.
Article
Chemistry, Physical
Andrea Luigi Sorrentino, Giulia Serrano, Lorenzo Poggini, Brunetto Cortigiani, Khaled E. El-Kelany, Maddalena D'Amore, Anna Maria Ferrari, Andrea Atrei, Andrea Caneschi, Roberta Sessoli, Matteo Mannini
Summary: Experimental and theoretical studies were conducted to investigate the structure and growth mechanism of TiO2 ultrathin films on Cu(001). It was found that a complete and flat TiO2 bilayer with a lepidocrocite-like structure is observed at the earliest stages of growth on the Cu(001) surface. Ab initio calculations confirmed that the lepidocrocite-like structure is thermodynamically more stable on Cu(001) than the quasi-hexagonal structure, leading to the observed transition.
JOURNAL OF PHYSICAL CHEMISTRY C
(2021)
Article
Physics, Applied
Kali Prasanna Mondal, Sambhunath Bera, Ajay Gupta, Dileep Kumar, Anil Gome, V. Raghavendra Reddy, Nobuaki Ito, Yukiko Yamada-Takamura, Pallavi Pandit, Stephan Roth
Summary: The study investigated the structural and morphological characteristics of Alq(3) thin films deposited at different rates using XRR and GISAXS. Slowing down the deposition rate increased the electron density, reduced defects and porosity, and decreased the diffusion depth of Co in Alq(3). This suggests that controlling the growth rate of Alq(3) can improve the performance of organic spin valve devices.
JOURNAL OF PHYSICS D-APPLIED PHYSICS
(2021)
Article
Physics, Condensed Matter
Debi Garai, Vladyslav Solokha, Axel Wilson, Ilaria Carlomagno, Ajay Gupta, Mukul Gupta, V. Raghavendra Reddy, Carlo Meneghini, Francesco Carla, Christian Morawe, Jorg Zegenhagen
Summary: This work presents a novel approach for studying surface processes of stainless steel during galvanic corrosion using ultra-thin films and synchrotron x-radiation. The films, deposited from austenitic steel, were found to be representative replicas of the target material. By monitoring material transport and leaching of Fe and Ni, the study provides insights into the early stages of corrosion events.
JOURNAL OF PHYSICS-CONDENSED MATTER
(2021)
Article
Engineering, Electrical & Electronic
Jagrati Dwivedi, Mukul Gupta, V. R. Reddy, Ashutosh Mishra, Pallavi Pandit, Ajay Gupta
Summary: Anomalous behavior of magnetic anisotropy in Co40Fe43B17 film sandwiched between Mo layers is observed during thermal annealing at different temperatures. The as-deposited amorphous film exhibits a uniaxial magnetic anisotropy due to quenched-in stresses. Anomalous magnetic reversal near the hard axis is observed in samples annealed at 350 degrees C and above, which can be explained by the distribution of easy magnetization direction evidenced by the ripple domain structure in Kerr microscopy images.
IEEE TRANSACTIONS ON MAGNETICS
(2021)
Article
Materials Science, Multidisciplinary
Yasmeen Jafri, Gagan Sharma, Ajay Gupta, Mukul Gupta, V. R. Reddy
Summary: This study investigated the magnetic properties of ferromagnetic films composed of Co and Fe interfaced with Ta using MOKE, XRR, and SXAS. The evolution of magnetic properties with increasing film thickness was studied, showing a thickness-dependent magnetic anisotropy for Co but not for Fe. The coercivity variation with film thickness was in agreement with the observed changes in magnetic anisotropy.
Article
Nanoscience & Nanotechnology
S. R. Kumar, D. M. Phase, Ajay Gupta, A. C. Pandey, Ratnesh Gupta
Summary: The study synthesized ferromagnetic Co-doped TiO2 thin films at room temperature using RF sputtering and ion irradiation with 100 MeV Au ions. Increasing Au-ion fluence results in higher surface roughness of the film and alters its magnetic properties.
Article
Materials Science, Multidisciplinary
Yasmeen Jafri, Surendra Singh, Surbhi Gupta, Yasuhiro Fukuma, Kavita Sharma, Mukul Gupta, V. R. Reddy, Gagan Sharma, Ajay Gupta
Summary: The study investigated the temperature dependent magnetic, structural, and electronic properties of FeTa films with increasing Ta concentration. It was found that densification of the film and increased electron density occurred with increasing Ta concentration. The presence of Ta in grain boundary region inhibited grain growth, leading to an increase in magnetic coercivity and decreased effective magnetic moment with increasing Ta concentration.
JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS
(2021)
Article
Physics, Condensed Matter
Niti, Yogesh Kumar, Seema, V. R. Reddy, Joseph Vimal Vas, Surbhi Gupta, Jochen Stahn, Ajay Gupta, Mukul Gupta
Summary: This work investigates the effect of Ag doping on the phase formation of FeN thin films and finds that Ag doping at around 5 at.% not only improves the thermal stability of FeN but also reduces intrinsic defects. The study shows that Ag doping reduces Fe self-diffusion in FeN by occupying grain-boundary positions as nanoparticles.
JOURNAL OF PHYSICS-CONDENSED MATTER
(2022)
Article
Materials Science, Multidisciplinary
Ratnesh Gupta, K. Sangeeth, M. Gupta, R. J. Choudhary, A. Sagdeo, F. Singh, Ajay Gupta
Summary: The FeCo/CoO bilayer shows exchange bias at 10K, with the value being enhanced by thermal annealing. X-ray diffraction confirms the phase formation in the CoO layer, and a correlation is observed between soft X-ray absorption and magnetic characteristics. Ion irradiation affects the exchange bias value, with higher ion fluence reducing the value due to defects in the film.
APPLIED PHYSICS A-MATERIALS SCIENCE & PROCESSING
(2022)
Article
Chemistry, Physical
Pramod Vishwakarma, Maheswar Nayak, V. R. Reddy, Andrei Gloskovskii, Wolfgang Drube, Ajay Gupta
Summary: The characteristics of the interfaces in the magnetic layer of the heterostructure Ta/Co2FeAl/MgO have been studied using HAXPES. It has been observed that the behavior of Co and Fe at the interfaces is different, with a higher percentage of Fe being oxidized or alloyed. The oxidation state of both Co and Fe decreases as the distance from the MgO interface increases, and Fe is further oxidized and Co is partially reduced after thermal annealing.
APPLIED SURFACE SCIENCE
(2022)
Article
Chemistry, Physical
Harsh Vardhan, Surendra Singh, Surbhi Gupta, Kavita Sharma, Yasmeen Jafri, Mukul Gupta, V. R. Reddy, R. S. Rawat, Ajay Gupta, Anil Gome, Gagan Sharma
Summary: This study provides an example of tailoring magnetic properties by structural modifications with controlled incorporation of Ta in soft magnetic CoFeB films. Unlike conventional thermal annealing, the stress-induced in-plane uniaxial magnetic anisotropy of CoFeB is released with the incorporation of Ta. The increase in atomic percent of Ta in CoFeB leads to a decrease in the saturation magnetization of the soft magnetic layer and film densification. Ferromagnetic resonance confirms the reduction of effective magnetization and the increase in damping parameter due to the presence of Ta. Vacuum annealing rapidly eliminates the magnetic anisotropy in Ta-doped CoFeB films, and annealing at a temperature beyond the CoFeB crystallization temperature increases the magnetization and magnetic coercivity.
JOURNAL OF ALLOYS AND COMPOUNDS
(2022)
Article
Materials Science, Multidisciplinary
Shubham Kumar, V. Srihari, Gagan Sharma, Ajay Gupta, V. R. Reddy, Mukul Gupta, Anil Gome, Kavita Sharma
Summary: Enhanced L10 ordering kinetics, improved crystallographic texturing in [001] direction, and high magnetic coercivity of about 6 kOe are observed in L10 ordered Fe(1-x)CuxPt films after successive isochronal vacuum annealing of multilayer structures. GIXRD measurements validate the onset of L10 ordering and the presence of high degree of ordering. GIXRD measurements also confirm the texturing of the magnetic easy axis [001] in the out of film plane direction. The addition of Cu and the annealing temperature have systematic effects on the structural and magnetic properties of Fe(1-x)CuxPt films, leading to enhanced kinetics and texturing effects of L10 FePt.
JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS
(2023)
Article
Chemistry, Physical
Debmalya Roy, B. Vaishnav, Sarathlal Koyiloth Vayalil, Ajay Gupta, N. Eswara Prasad, Benedikt Sochor, Matthias Schwartzkopf, Stephan V. Roth, Tobias Kraus
Summary: This study investigates a major limitation of flexible sensors, namely the loss of conductivity upon multiple stretching and bending cycles. The researchers introduce conducting fillers with two different geometries, carbon black and carbon nanotubes, into polydimethylsiloxane (PDMS) to understand the effect of periodic tensile stress on the structure formation of nanofillers. The results show that loading the nanofillers beyond the percolation threshold ensures cyclic stability of the resulting network channels. In addition, they vary the surface chemistry of the carbon nanotubes to investigate interfacial interactions at the molecular level.
JOURNAL OF PHYSICAL CHEMISTRY LETTERS
(2023)
Article
Materials Science, Multidisciplinary
Pramod Vishwakarma, Gagan Sharma, M. H. Modi, Mukul Gupta, Jochen Stahn, Ajay Gupta
Summary: The migration of boron in CoFeB/MgO multilayer during the amorphous to crystalline transformation in CoFeB has been investigated using Polarized Neutron Reflectivity (PNR) and anomalous Soft X-ray Reflectivity (SXR). Both PNR and anomalous SXR results indicate that boron tends to move away from the MgO/CoFeB interfaces and forms a boride layer in the middle of the magnetic layer upon thermal annealing. These findings are significant for understanding the role of boron in CoFeB/MgO based magnetic tunnel junctions.
MATERIALS RESEARCH BULLETIN
(2023)
Proceedings Paper
Materials Science, Multidisciplinary
Yasmeen Jafri, Surendra Singh, Gagan Sharma, Kavita Sharma, Mukul Gupta, V. R. Reddy, Ajay Gupta
Summary: The thickness dependent structural and magnetic properties of Co films interfaced with Hf were investigated. XRR and GIXRD were used to analyze the structural properties of deposited samples. The magnetic properties of samples were studied as a function of Co film thickness using MOKE and PNR. The results showed that the magnetic coercivity and effective magnetic moment varied with Co film thickness, and a magnetically dead layer was observed at the interface.
MATERIALS TODAY-PROCEEDINGS
(2022)
Proceedings Paper
Materials Science, Multidisciplinary
Shubham Kumar, Kavita Sharma, Gagan Sharma, Ajay Gupta, V. Raghavendra Reddy, Anil Gome, Sadhan Chandra Das
Summary: Fe100-xPtx alloy films were fabricated by controlled ion beam sputtering, and the evolution of L10 ordering during annealing was studied. The findings have implications for the fabrication of future recording media materials.
MATERIALS TODAY-PROCEEDINGS
(2022)
