Magnetic Properties Research Articles

Corrosion resistance enhancement of bulk metallic glass through ultrasonic vibrations

Bulk metallic glass (BMG) possesses a range of desirable properties, including exceptional mechanical, soft magnetic, and catalytic properties, etc. However, to pursuit extensive specific applications, enhancing the corrosion resistance of BMG is required. Herein, an effective method involving ultrasonic vibrations (UV) treatment was proposed to significantly enhance the corrosion resistance of BMG. The self-corrosion potential of UV processed BMG increased by up to 0.14 V in 1 N HCl solution and 0.2 V in 3.5 % NaCl solution, respectively. Additionally, the maximum reduction in corrosion current density for the UV processed BMG in these solutions was 15 % and 20 %, respectively. Micro-morphology results indicated that the UV processed BMG exhibited better pitting resistance. It is found that a denser arrangement of BMG was obtained after UV which resulted in reduced relaxation enthalpy and enhanced corrosion resistance. This work introduces an innovative and convenient method to enhance the corrosion resistance of BMG for engineering applications.

Development of a magnetic separation method for rapid isolation and enrichment of bacteria in raw pork using chitosan functionalized magnetic Fe3O4@MIL-100(Fe) composites.

In this study, a pretreatment method based on a magnetic capture probe for the rapid isolation and enrichment of bacteria from raw pork was developed. The chitosan immobilized Fe3O4@MIL-100(Fe) was prepared as a capture probe for total bacterial counts through the electrostatic interaction of positively charged chitosan and the negatively charged substances on the surface of bacteria. The interference of matrix in pork samples on this method was studied and removed by differential centrifugation. The results showed the capture probe had a great selectivity binding and magnetic separation properties for the tested six common bacteria in pork. Under the optimal conditions, the capture efficiency of the bacteria (105 CFU mL-1) from pork surface samples was all above 90%. The capture efficiency of the bacteria in a homogenate system was greatly decreased due to the interference of sarcoplasmic protein and myofibrillar protein in pork. The matrix effect was mitigated by a differential centrifugation method, and the capture efficiency of all six bacteria was >80%. The developed magnetic separation method took 40min and showed good isolation and enrichment properties of bacteria. Thus, the proposed method is expected to provide a simple, convenient, and time-saving pretreatment method for the detection of total bacterial counts in pork.

Investigation of the electronic, optical and magnetic properties of a novel two-dimensional lead-free perovskite: High visible-light absorption and long-range magnetic ordering.

Recently, big issues that need to be solved in photovoltaic solar cells area are the toxicity and instability of lead halide perovskites which have shown exceptional photoelectric performances. Herein, we report the synthesis and physico-chemical characterization of a novel two-dimensional (2D) lead-free perovskite. The 2D Cu(II)-based perovskite (C4N3H16)[CuCl4]∙Cl was successfully stabilized by the slow evaporation method under room temperature. The X-ray diffraction shows a layered structure with an inorganic network formed by four corners sharing CuCl6 octahedra. The UV-Vis absorption analysis confirms the manifestation of the cooperative Jahn-Teller effect around the Cu(II) ions. In addition to the ligand-to-metal charge transfer transitions, crystal field transitions (d-d) enhance the visible-light absorbance and make the material suitable for green solar cell applications with a band gap energy of 2.17 eV. The thermal analysis revealed the thermal stability of (C4N3H16)[CuCl4]∙Cl. Magnetic measurements revealed the presence of dominant ferromagnetic exchange interactions with J/kB = 22.85 K within the 2d planes, with a weak antiferromagnetic exchange interaction yielding a long-range magnetic ordering at 12 K.

Magnetic properties of binary alloys Ni[formula omitted]Mo[formula omitted] and Ni[formula omitted]Cu[formula omitted] close to critical concentrations

The search for the ferromagnetic quantum critical point (FM QCP) has always been a captivating research topic in the scientific community. In pursuit of this goal, we introduced nonmagnetic transition metals to alloy with elemental nickel, and studied the magnetic properties of nickel binary alloys Ni1−xMox and Ni1−yCuy as a function of x and y up to the critical concentrations xcr and ycr at which the FM transition TC disappears. TC−x(y) phase diagrams were constructed via the Arrott–Noakes scaling of magnetization data. An enhanced Sommerfeld coefficient (the value of C/T as T→0) is observed near xcr and ycr, manifesting the effect of quantum fluctuations. However, the spin glass behavior is identified through the ac magnetic susceptibility measurements. This observation rules out the possibility of the existence of the FM QCP in both systems.

Customizable Induction Heating Profiles: from Tailored Colloidally Stable Nanoparticles Toward Multi‐Stage Heatable Supraparticles

AbstractMagnetic nanoparticles (NPs) are efficient heat mediators in induction heating. Originally explored for hyperthermia, their applications have broadened to industrial processes where temperature control is crucial. By adjusting the NP composition or morphology, magnetic characteristics such as Curie temperatures can be tailored, allowing control over maximum heating thresholds. These NPs are, however, usually designed for maximum heating rates at specific magnetic fields. In this work, the synthesis is presented for colloidally stable Co and ZnCo ferrite NPs with customizable maximum heating temperatures, and their combination within micron‐scaled supraparticles (SPs). Maximum induction heating temperatures of ZnCo ferrite NPs are tuned between 150 and 220 °C, while customization of Co ferrite species yields temperatures between 200 and 350 °C. These distinct magnetic properties are exploited in the selective multi‐stage heating of SPs consisting of both species. Here, ZnCo ferrite components heat up to a first temperature plateau at low alternating magnetic fields (AMF), while Co ferrite NPs reach higher temperatures at increased AMF. The precise control of induction heating thresholds through the adaptability of NPs offers a high degree of customizability which makes induction heating particularly attractive for applications requiring sequential or spatial heating, such as catalysis or debonding on demand.

Barrier heights and strong fermi-level pinning at epitaxially grown ferromagnet/ZnO/metal Schottky Interfaces for opto-spintronics applications

Schottky contacts at the ferromagnet/ZnO interface are good candidates for the realization and control of several semiconductor emerging magnetic phenomena such spin injection and spin-controlled photonics. In this work, we demonstrate the epitaxial growth of single-phase and wurtzite-ZnO thin films on fcc Pt/Co0.30Pt0.70 (111) electrodes by molecular beam epitaxy technique. While the magnetic properties of the Pt/Co0.30Pt0.70 buffer remain unchanged after the ZnO growth, the electric measurements of back-to-back Schottky diodes reveal Schottky barrier heights at the metal/ZnO interfaces in the range of 590–690 meV using Cu, Pt and Co0.30Pt0.70 contacts. A pinning factor S and a charge neutrality level (CNL) ΦCNL of 0.08 and 4.94 eV, respectively, are obtained indicating a strong Fermi-level pining with a CNL level that lies 0.64 eV bellow the conductance band of ZnO semiconductor. These experimental findings indicate that Co0.30Pt0.70/ZnO interface follows the metal-induced gap states model and can open a pathway for the realization of opto-spintronics applications such spin-LEDs.

Low Temperature Plasma-Assisted Double Anodic Dissolution: A New Approach for the Synthesis of GdFeO3 Perovskite Nanoparticles.

Orthorhombic perovskite GdFeO3 nanostructures are promising materials with multiferroic properties. In this study, a new low-temperature plasma-assisted approach is developed via dual anodic dissolution of solid metallic precursors for the preparation of perovskite GdFeO3 nanoparticles (NPs) that can be collected both as colloids as well as deposited as a thin film on a substrate. Two solid metallic foils of Gd and Fe are used as precursors, adding to the simplicity and sustainability of the method. The formation of the orthorhombic perovskite GdFeO3 phase is supported by high-resolution transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and Raman measurements, while a uniform elemental distribution of Gd, Fe, and O is confirmed by energy dispersive X-ray spectroscopy, proving the successful preparation of ternary compound NPs. The magnetic properties of the NPs show zero remnant magnetization typical of antiferromagnetic materials, and saturation at high fields that can be caused by spin interaction between Gd and Fe magnetic sublattices. The formation mechanism of ternary compound NPs in this novel plasma-assisted method is also discussed. This method is also modified to demonstrate the direct one-step deposition of thin films, opening up opportunities for their future applications in the fabrication of magnetic memory devices and gas sensors.

Half‐Metallic Ferromagnetism in 2D Janus Monolayers: Mn2GeX (X = As, Sb)

Two‐dimensional (2D) Janus materials are a fascinating class of materials resulting from their unique electronic and magnetic properties induced by mirror symmetry breaking. However, 2D Janus materials with intrinsic magnetism remain rather rare, casting a mysterious veil over magnetism. In this work, the electronic and magnetic properties of Janus Mn2GeX (X = As, Sb) monolayers using the first‐principles calculations are investigated. The results demonstrate that these Janus materials exhibit excellent mechanical and dynamic stability, indicating their potential for future applications in nanoscale spintronic devices. Interestingly, the Janus and monolayers possess exciting half‐metallic character with wide half‐metallic gaps of 0.29 and 0.18 eV, and spin gaps of 1.68 and 1.62 eV, respectively. Their calculated ground state exhibits a strong preference for ferromagnetic ordering, with a Curie temperature () of 630 and 590 K, respectively. Additionally, the ferromagnetism of Janus Mn2GeX (X = As, Sb) monolayers is robust against biaxial strain ranging from −6% to 6%. Under 6% tensile strain, the calculated of the monolayer is 639 K, which represents a 9% increase compared to the observed in the unstrained condition. All these intriguing electronic and magnetic properties make the Janus Mn2GeX (X = As, Sb) monolayers an appealing candidate for applications in nanoscale spintronic devices.

Spin chain orientation and magneto-optical coupling in twisted NiPS3 homostructures

Magnetic two-dimensional (2D) materials have garnered significant attention due to their unique electronic, magnetic, and optical properties and their potential applications in next-generation electronic and optoelectronic devices. However, the magneto-optical effects of oligolayer antiferromagnetic materials remain inadequately understood. Here, we investigate the magnetic properties of few-layer nickel phosphorus trisulfide (NiPS3) and its twisted heterostructures, emphasizing the observation of optical phenomena at low temperatures (1.65 K). By stacking few-layer NiPS3 to fabricate twisted homostructures, we probe their magnetic characteristics using photoluminescence (PL) spectroscopy. Our results reveal that sharp exciton peaks emerge at low temperatures and that the spin chain orientation in oligolayer NiPS3 can be discerned through the polarization dependence of exciton PL intensity. Notably, fewer-layered NiPS3 exhibits a significant magneto-optical effect under an applied magnetic field, allowing the modulation of the polarization angle of its exciton PL spectrum. Additionally, the polarization-dependent Raman spectrum of NiPS3 shows substantial changes under the influence of a magnetic field. These findings underscore the potential of few-layer NiPS3 for future magneto-optical device applications.

Classical spin models and basic magnetic interactions on 1/1-approximant crystals

We study classical spin models on the 1/1 Tsai-type approximant lattice using Monte Carlo and mean-field methods. Our aim is to understand whether the phase diagram differences between Gd- and Tb-based approximants can be attributed to anisotropy induced by the crystal-electric field. To address this question, we treat Gd ions as Heisenberg spins and Tb ions as Ising spins. Additionally, we consider the presence of the Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction to replicate the experimentally observed correlation between magnetic properties and electron concentration. Surprisingly, our findings show that the transition between ferromagnetic and antiferromagnetic order remains unaltered by the anisotropy, even when accounting for the dipole interaction. We conclude that a more comprehensive model, extending beyond the free-electron gas RKKY interaction, is likely required to fully understand the distinctions between Gd- and Tb-based approximants. Our work represents a systematic exploration of the impact of anisotropy on the ground-state properties of classical spin models in quasicrystal approximants. Published by the American Physical Society 2024

A New Approach to Single‐Step Fabrication of TiOx‐CeOx Nanoparticles

Mixed metal oxide (MMO) nanoparticles (NPs) are hybrids consisting of two or more nanoscale metal oxides. Advantages of MMO NPs over single metal oxides include improved catalytic activity, enhanced electrical and magnetic properties, and increased thermal stability due to the synergy of the different oxide components. This study presents a novel fabrication route for TiO2‐CeO2 NPs enriched with oxygen vacancies using a Haberland‐type gas aggregation cluster source. The NPs, deposited from different segmented Ti/Ce targets under varying O2 addition, were examined with respect to final composition, morphology, and Ti, Ce surface oxidation states. Particle formation mechanisms are proposed for the observed morphologies. Additionally, available O2 during deposition and its impact on the formation of defective sites were investigated. Defective sites in TiO2‐CeO2 NPs were analyzed using transfer to X‐ray photoelectron spectroscopy and transmission electron microscopy without contact to ambient oxygen. The incorporation of Ce to the target exhibits synergistic effects on the synthesis process. Segmented Ti/Ce targets enable the deposition of a broad range of mixed oxide NPs with diverse compositions and morphologies at considerably enhanced deposition rates, which is vital for practical applications. The presented fabrication approach is expected to be applicable for a broad variety of MMO NPs.

Studying the structural, magnetic, and dielectric properties of cobalt-substituted R- type hexaferrites

Studying the structural, magnetic, and dielectric properties of cobalt-substituted R- type hexaferrites

Effective control of magnetism and transport properties of monolayer WV2N4 with two magnetic atomic layers and its van der Waals heterostructure

The large magneto-resistance (MR) effect produced by electric control of the magnetic state for van der Waals (vdW) heterostructures composed of vdW intrinsic magnets holds great significance for low-dissipation spintronic devices. Our first-principles calculations reveal that the proposed monolayer WV2N4 is a ferromagnetic (FM) metal with two magnetic V atomic layers, and the interlayer magnetic coupling between two V atomic layers can be switched from FM to antiferromagnetic coupling by applying a small compressive strain. Interestingly, a large MR ratio of 253% is achieved in the proposed graphite/monolayer WV2N4/graphite vdW heterostructure using a −1.5% compressive strain. Combining the strain-induced change in magnetism of monolayer WV2N4 and the graphite/monolayer WV2N4/graphite vdW heterostructure with the inverse piezoelectricity of piezoelectric materials, a feasible strategy is proposed to achieve electric control of the interlayer magnetic coupling of monolayer WV2N4 in the graphite/monolayer WV2N4/graphite vdW heterostructure clamped by piezoelectric materials by utilizing the inverse piezoelectricity, thereby generating a large MR ratio in the graphite/monolayer WV2N4/graphite vdW heterostructure clamped by the piezoelectric material. Our work presents a promising avenue for developing energy-efficient spintronic devices.

Effect of Transition Metal (Gd, Dy) Co-doping on Structural, Optical, and Magnetic Properties of CeO2 Nanoparticles by Solid-State Reaction

Effect of Transition Metal (Gd, Dy) Co-doping on Structural, Optical, and Magnetic Properties of CeO2 Nanoparticles by Solid-State Reaction

Martensitic transformations and magnetic properties of Ni50−xMn37Sn13Fex(x = 0.5, 1, 1.5) melt-spun ribbons

AbstractThe present study investigates the influence of iron (Fe) doping on the martensitic transformation and magnetic properties of Ni50−xMn37Sn13Fex(x = 0.5, 1, 1.5) magnetic shape memory alloys in ribbon form. The ribbons were prepared using arc-melting followed by melt-spinning processes and were characterized using X-ray diffraction, scanning electron microscopy, differential scanning calorimetry, and vibrating sample magnetometry. Our findings demonstrate that the addition of Fe shifts the martensitic transformation to lower temperatures and increases the Curie point of the austenitic phase, $$T_{c}^{\text A}$$ T c A , leading to an enhanced magnetism in the austenitic phase. Moreover, a significant increase in the magnetization jump $$(\Delta M)$$ ( Δ M ) is observed, from $$ 3.3\;{\text{emu\ g}}^{-1} $$ 3.3 emu\ g - 1 for $$x=1$$ x = 1 to $$17 \, {\text{emu\ g}}^{-1} $$ 17 emu\ g - 1 for $$x=1.5$$ x = 1.5 under a $$50 \, \text {Oe}$$ 50 Oe applied magnetic field. The structural transformations are also found to be sensitive to the external applied magnetic field. The isothermal magnetization curves exhibit the exchange bias effect, which confirms the coexistence of antiferromagnetic and ferromagnetic coupling in the samples. Furthermore, the exchange bias effect increases with the Fe content.

Influence of local structure and metal-oxygen hybridization on the electrical and magnetic properties of alkaline earth metal (Mg2+, Ca2+, Sr2+) substituted LaFeO3 ceramics

Pristine and alkaline-earth metal-substituted LaFeO3 (La1−xAxFeO3−δ; x = 0 and 0.2; A = Mg2+, Ca2+, and Sr2+) sintered ceramics are prepared from nanoparticles synthesized via a low-temperature citrate sol–gel technique. X-ray diffraction studies confirm the formation of a phase-pure LaFeO3 structure without any secondary phases for all the La1−xAxFeO3−δ compositions. LaFeO3 and La0.8Mg0.2FeO3−δ ceramics show Raman active modes related to La vibration, oxygen octahedral tilting, bending, and stretching. The optical bandgap is estimated to be 2.34 eV for pure LaFeO3 and reduces to 2.23 eV for La0.8Mg0.2FeO3−δ ceramics. On the contrary, La0.8Ca0.2FeO3−δ and La0.8Sr0.2FeO3−δ ceramics show no features in Raman spectra, consistent with the observation of metallic nature and diffuse band edge without any indication of sharp band edge noted. X-ray absorption spectroscopy (XAS) studies on La-L3 and Fe-K-edges confirm the oxidation states of La3+ and Fe3+ in all these ceramics. Local structural distortions and formation of oxygen vacancies in La0.8A0.2FeO3−δ (A = Mg2+, Ca2+, and Sr2+) ceramics are discerned from XAS structure analysis compared to the pristine LaFeO3 ceramics. Magnetic measurements of La1−xAxFeO3−δ reveal weak ferromagnetic nature except for La0.8Mg0.2FeO3−δ, which shows a large magnetization of 4.6 (6.7) emu/g at 300 (5) K. The ferromagnetic behavior of La0.8Mg0.2FeO3−δ ceramics seems to originate from the modification of hybridization between Fe(3d)–O(2p), La(5d)–O(2p), and Fe(4sp)–O(2p) orbitals. An anomalous magnetic transition observed only in zero-field-cooled curves at 88 K in La0.8Ca0.2FeO3−δ and La0.8Sr0.2FeO3−δ ceramics is correlated to the formation of new electronic states containing O 2p character as discerned from pre-peak O-K-edge.

First-principles study on the electronic structure, magnetic and optical properties of strain regulated (V, Mn) co-doped HfS2 monolayer

The impact of biaxial strain on the electronic structure, magnetic and optical properties of double impurity co-doped HfS2 monolayers was investigated using first principles methods. The findings indicate that (V, Mn) co-doped HfS2 monolayer behaves as a dilute magnetic semiconductor both before and after the application of strain, with its magnetism attributed to the hybridization of V:3d, Mn:3d, and S:3p orbitals. In the biaxial strain range of −5% to 5%, the ferromagnetism remains unchanged, the band gap decreases with the increase of compressive strain. In contrast, tensile strain leads to an increase in both the band gap. Finally, our analysis of optical properties reveals that (V, Mn) co-doped HfS2 monolayer enhances infrared light absorption coefficient, compressive strains further enhance this absorption coefficient. These results indicate that (V, Mn) co-doped HfS2 monolayer by strain regulation is an effective strategy for designing dilute magnetic semiconductors and optoelectronic devices.

Enhanced peroxidase‐like activity of MnFe2O4 nanoparticles on halloysite nanotubes for uric acid detection

AbstractNanozymes have significantly advanced sensing assays by replicating native enzyme functions. However, designing nanozymes with high catalytic activity and easy recyclability remains challenging. The study presented here has resulted in the development of a highly efficient and sensitive colorimetric system for the detection of uric acid, utilizing MnFe2O4@HNTs—a novel composite material consisting of MnFe2O4 loaded onto halloysite nanotubes. These nanocomposites exhibited outstanding peroxidase‐like activity and attractive magnetic properties. The catalytic efficiency of the MnFe2O4@HNTs in the oxidation of 3,3′,5,5′‐tetramethylbenzidine, in the presence of H2O2, was remarkable, leading to a distinct color change from colorless to blue. A linear relationship was observed between absorbance and UA concentration in the range of 1–20 μM, with a detection limit as low as 52 nM. Mechanistic investigations revealed that reactive oxygen species (ROS), specifically singlet oxygen (1O2), were generated through the decomposition of H2O2, which is responsible for the peroxidase‐like activity demonstrated by the MnFe2O4@HNTs. The method showed minimal interference from serum substances and high selectivity. Magnetic MnFe2O4 allowed easy separation and maintained over 95% activity after seven reuse cycles. The developed assay was successfully applied to the detection of uric acid in human serum, achieving recoveries greater than 98.60%. This research significantly advances the design of recyclable high‐performance nanozymes and establishes an effective colorimetric sensing platform for UA detection in clinical samples, potentially improving diagnostic tools for healthcare applications.

Effects of interfacial oxygen diffusion on the magnetic properties and thermal stability of Pd/CoFeB/Pd/Ta heterostructure

We investigated the effects of annealing temperatures (TA) on a Pd (5 nm)/CoFeB (10 nm)/Pd (3 nm)/Ta (10 nm) multilayer structure. The as-deposited sample showed an amorphous state with in-plane uniaxial magnetic anisotropy (UMA), resulting in low coercivity and moderate Gilbert damping constant (α) values. Increasing TA led to crystallization, forming bcc-CoFe (110) crystals, which increased in-plane coercivity and introduced isotropic magnetic anisotropy, slightly reducing the α. The two-fold UMA persists up to 600 °C, and the thermal stability of the in-plane magnetic anisotropy remains intact even TA = 700 °C. The TA significantly influenced the magnetic properties such as in-plane saturation magnetization (Ms//), in-plane and out-of-plane coercivities (Hc// and Hc⊥), and in-plane effective magnetic anisotropy energy density (Keff). Above 600 °C, Keff decreased, indicating a transition towards uniaxial perpendicular magnetic anisotropy. Interfacial oxidation and diffusion from the Ta capping layer to the Pd/CoFeB/Pd interfaces were observed, influencing chemical bonding states. Annealing at 700 °C, reduced oxygen within TaOx through a redox reaction involving Ta crystallization, forming TaB, PdO, and BOx states. Ferromagnetic resonance spectra analysis indicated variations in resonance field (Hr) due to local chemical environments. The α reduction, reaching a minimum at 300 °C annealing, was attributed to reduced structural disorder from inhomogeneities. Tailoring magnetic anisotropy and spin dynamic properties in Pd/CoFeB/Pd/Ta structures through TA-controlled oxygen diffusion/oxidation highlights their potential for SOT, DMI, and magnetic skyrmion-based spintronic devices.

Pseudocapacitive and Magnetic Properties of SrFe12O19–Polypyrrole Composites

This study is inspired by the importance of advanced composites, combining spontaneous magnetization with electrical charge storage properties. It is focused on the investigation of magnetically hard SrFe12O19 (SFO) material and its composites with polypyrrole (PPy). For the first time, an organic surfactant–charge transfer mediator and high-energy ball milling (HEBM) were applied to the preparation of high-active-mass SFO composite electrodes. An important finding was the ability to achieve enhanced capacitance of SFO and its composites in a negative range of electrode potentials in an electrolyte. The benefits of the sodium sulfate electrolyte and the charge storage mechanism are discussed. Another important finding was the synergy of the properties of SFO and PPy, which allowed the preparation of highly capacitive conductive composites. The effects of HEBM and the SFO content in the composites on the capacitive properties were studied. Magnetic measurements revealed the effect of HEBM on the magnetic properties and demonstrated good magnetic properties of the composites, which also exhibited advanced capacitive properties. The composites were utilized for the manufacturing of an asymmetric device, which exhibited high capacitive properties at an applied voltage of 1.5 V.