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At least 271 records · Page 15

Study of morphology and magnetic properties of the HoNi{sub 3} crystalline and ball-milled compound

The morphology and magnetic properties of the HoNi{sub 3} crystalline and ball-milled intermetallic compounds are presented. The polycrystalline HoNi{sub 3} bulk compound crystallizes in the rhombohedral PuNi{sub 3} — type of crystal structure and indicates ferrimagnetic arrangement with the Curie temperature of T{sub C} = 57 ± 2 K, the helimagnetic temperature T{sub h} = 23 ± 2 K with the total saturation magnetic moment of 6.84 μ{sub B}/f.u. at 2 K. The use of the ball-milling method leads to the formation of HoNi{sub 3} nanoflakes with typical thickness of less than 100 nm prone to agglomeration upon milling. The increase of grinding duration leads to the reduction in crystallite size, which was confirmed by various complementary microscopical and diffraction studies. Moreover, the increase in milling duration results in the emergence of the relatively small coercivity (H{sub C}), remanence (M{sub r}) and a variation of the saturation magnetization (M{sub S}). - Graphical abstract: Display Omitted - Highlights: • The ball-milling method exhibits significant potential for producing RT{sub 3} nanopowders. • The AFM method was used for the first time in analysis of R–T nanoflakes morphology. • HoNi{sub 3} compound forms polycrystalline and textured nanoflakes evolving upon milling. • The decrease in crystallite size via grinding is confirmed by XRD, TEM and AFM. • The magnetic parameters were sensitive to the extension of pulverization b.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

Structural and magnetic properties of the nanocomposite materials based on a mesoporous silicon dioxide matrix

The structural and magnetic properties of the mesoporous systems based on silicon dioxide with a regular hexagonal arrangement of pores several microns in length and several nanometers in diameter, which are filled with iron compound nanofilaments in various chemical states, are studied in detail. The studies are performed using the following mutually complementary methods: transmission electron microscopy, SQUID magnetometry, electron spin resonance, Mössbauer spectroscopy, polarized neutron small-angle diffraction, and synchrotron radiation diffraction. It is shown that the iron nanoparticles in pores are mainly in the γ phase of Fe{sub 2}O{sub 3} with a small addition of the α phase and atomic iron clusters. The effective magnetic field acting on a nanofilament from other nanofilaments is 11 mT and has a dipole nature, the ferromagnetic–paramagnetic transition temperature is in the range 76–94 K depending on the annealing temperature of the samples, and the temperature that corresponds to the change in the magnetic state of the iron oxide nanofilaments is T ≈ 50–60 K at H = 0 and T ≈ 80 K at H = 300 mT. It is also shown that the magnetization reversal of an array of nanofilaments is caused by the magnetostatic interaction between nanofilaments at the fields that are lower than the saturation field.

77 NANOSCIENCE AND NANOTECHNOLOGY↗

Effect of Fe and Ti Substitution Doping on Magnetic Property of Monolayer CrSi{sub 2}: a First-Principle Investigation

First-principle calculations based on spin-polarized density functional theory were performed to investigate the effect of Fe and Ti substitution doping on magnetic property of monolayer CrSi{sub 2}. The electronic structures, binding energy, magnetic property, total and partial density of states, and spin density of monolayer CrSi{sub 2} are scientifically studied. Calculated binding energy reveals that Fe-doped monolayer CrSi{sub 2} is more stable than Ti-doped monolayer CrSi{sub 2}. The local magnetic moment of Fe and Ti atom all decrease compared with atomic moment in free gas phase due to variation of bond interaction and charge transfer. The density of states and spin-density results indicated that local magnetic moment of Fe atom is larger than Ti atom, leading to total magnetic moment of Fe-doped monolayer CrSi{sub 2} is bigger than Ti-doped monolayer CrSi{sub 2}.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

Surface driven effects on magnetic properties of antiferromagnetic LaFeO{sub 3} nanocrystalline ferrite

LaFeO{sub 3} nanocrystalline ferrites were synthesized through sol-gel method in different size distributions and the effect of finite size on magnetic properties is investigated. Results of magnetization and Mössbauer measurements show that superparamagnetism and weak ferromagnetic behavior in some of the size distributions. The origin of the superparamagnetism is from fine particles similar to ferromagnetic single domains and the weak ferromagnetism comes from surface spin disorder caused by Dzyaloshinskii-Moriya interaction. The magnetic ground state of LaFeO{sub 3} nanoparticles differs from that of bulk, and the ground state is dictated by the finite size effect because density of states depends on the dimensionality of the sample.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

Magnetic properties and magnetocaloric effect in double Sr2FeMoO6 perovskites

Highlights: • Magnetocaloric effect in Sr2FeMoO6 is observed. • Room temperature magnetic refrigeration. • Double perovskite structure. • Sr2FeMoO6 used in magnetic refrigeration technology. • RCP and ΔS{sub m} of Sr{sub 2}FeMoO{sub 6} have been determined. - Abstract: The magnetic properties and magnetocaloric effect in Sr{sub 2}FeMoO{sub 6} compound have been studied using the Monte Carlo simulation. Thermal magnetization and dM/dT of Sr{sub 2}FeMoO{sub 6} are given. The Curie temperatures T{sub C}(K) have been obtained. The temperature dependence of the magnetic entropy for a several magnetic field have been also obtained. The field dependence of relative cooling power and magnetic hysteresis cycle of Sr{sub 2}FeMoO{sub 6} have been determined for a several magnetic field and temperatures. The Sr{sub 2}FeMoO{sub 6} might be a promising base for developing the new kinds of magnetic refrigerant as working materials in magnetic refrigeration technology.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

Ellipsometric investigation of ZnFe{sub 2}O{sub 4} thin films in relation to magnetic properties

We report an influence of disorder on structural and magnetic properties of ZnFe{sub 2}O{sub 4} thin films grown at temperatures ranging from 400 °C to 600 °C by pulsed laser deposition in O{sub 2} atmosphere on SrTiO{sub 3} (100) substrates evidenced by properties of electronic transitions observed in the dielectric function. Inversion of the normal spinel structure was found to be one of the main mechanisms responsible for the increase in the magnetic response for the lowest growth temperature. The enhanced feature in the dielectric function located at ∼3.5 eV, related to the transition involving tetrahedrally coordinated Fe{sup 3+} cations, corresponds to the dominating magnetic coupling between the octahedral and tetrahedral lattice sites, responsible for the overall ferrimagnetic behaviour of the film grown at the lowest temperature.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

Magnetic Properties Tuning via Broad Range Site Deficiency in Square Net Material UCu x Bi 2

HfCuSi 2 -type pnictogen compounds have recently been shown to be a versatile platform for designing materials with topologically nontrivial band structures. However, these phases require strict control over the electron count to tune the Fermi level, which can only be achieved in compositions with A 2+ M 2+ Pn 2 and A 3+ M + Pn 2 (A = lanthanides, M = transition metals, Pn = pnictogens P–Bi) charge distribution. While such lanthanide compounds have been thoroughly studied as candidate magnetic topological materials, their heavy element analogs with uranium and bismuth remain largely underexplored. In this report, we present the synthesis of UCu x Bi 2 single crystals and study their magnetic properties. Detailed structural analysis revealed that flux-grown crystals always form as a site-deficient UCu x Bi 2 composition, where x varies between 0.20 and 0.64. Magnetic property measurements revealed a dependence of the magnetic coupling on the Cu site deficiency, linearly changing the Néel temperature from 51 K for UCu 0.60 Bi 2 to 118 K for UCu 0.30 Bi 2 . Moreover, higher Cu concentration promotes a metamagnetic transition in highly magnetically anisotropic UCu 0.60 Bi 2 single crystals. We show that DFT calculations can successfully model site deficiency in the UCu x Sb 2 and UCu x Bi 2 systems. This work paves the way toward using the site deficiency to tune the Fermi level in more ubiquitous A 3+ M 2+ x Pn 2 phases, which previously have not been considered topological candidate materials due to unfavorable electron count.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

Magnetic properties and coercivity mechanism of Sm{sub 1-x}Pr{sub x}Co{sub 5} (x=0-0.6) nanoflakes prepared by surfactant-assisted ball milling

Sm{sub 1-x}Pr{sub x}Co{sub 5} (x=0-0.6) nanoflakes with CaCu{sub 5} structure were successfully prepared by surfactant-assisted high-energy ball milling (SAHEBM). The crystal structure and magnetic properties of Sm{sub 1-x}Pr{sub x}Co{sub 5} (x=0-0.6) nanoflakes were studied by X-ray diffraction and vibrating sample magnetometer. Effects of Pr addition on the structure, magnetic properties and coercivity mechanism of Sm{sub 1-x}Pr{sub x}Co{sub 5} nanoflakes were systematically investigated. XRD results show that all the nanoflakes have a hexagonal CaCu{sub 5}-type (Sm, Pr){sub 1}Co{sub 5} main phase and the (Sm, Pr){sub 2}Co{sub 7} impurity phase, and all of the samples exhibit a strong (00l) texture after magnetic alignment. As the Pr content increases, remanence firstly increases, then slightly reduced, while anisotropy field (H{sub A}) and H{sub ci} of decrease monotonically. Maximum energy product [(BH){sub max}] of the flakes increases first, peaks at 24.4 MGOe with Pr content of x = 0.4, then drops again. Magnetization behavior analysis indicate that the coercivity mechanism is mainly controlled by inhomogeneous domain wall pinning, and the pinning strength weakens with the increased Pr content, suggesting the great influence of H{sub A} on the coercivity of flakes.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

Magnetic Properties of Electroformed Ni and Ni-Fe for Micromagnetic MEMS Applications

This paper reports a new technique which is based on electroforming process for high permeability Ni and Ni-Fe alloy. The magnetic properties of Ni and Ni-Fe alloy are investigated as a function of plating current density via scanning electron microscope (SEM), energy dispersive spectroscopy (EDS), and vibrating sample magnetometer (VSM). Concentration-dependent kinetics is used to formulate the deposition rate and also the same is verified by using finite element analysis tool COMSOL Multiphysics. Several experiments are performed to derive the relation between electroplating parameters and magnetic properties. The process conditions are optimized to develop high permeability (∼16000) Ni-Fe alloy (85.71–14.29 %). The higher current density shows a monotonically increasing behavior of relative permeability (μ{sub r}). In addition, the B-H curves indicate that the saturation magnetization (B{sub sat}) increases and coercivity decreases with increasing plating current density. Our experimental data confirms that the higher current density increase the softness of Ni. The observed properties of Ni and Ni-Fe based on experimental results can be used to study the magnetic behavior of micromagnetic sensors and large force actuators.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

Influence of Ba Substitutions on Microstructure and Magnetic Properties of La–Ca–Co System Permanent Ferrite

La{sub 0.6}Ca{sub 0.4−x}Ba{sub x}O⋅n/2(Fe{sub 1−y}Co{sub y}){sub 2}O{sub 3}(x = 0, 0.05, 0.1, 0.15 and 0.2) permanent ferrite materials were prepared by ceramic technique. The topography and the structure were characterized by scanning electron microscopy (SEM) and x-ray diffraction (XRD), respectively. The magnetic properties were measured using vibrating sample magnetometer (VSM) and digital magnetometer. Single M-phase and flake-like grains were obtained for samples without Ba substitution(x = 0), and the magnetic properties of the pre-sintering La–Ca–Co ferrite were as follows: B{sub r} = 440 mT, H{sub cb} = 296 kA/m, H{sub cj} = 426 kA/m, (BH){sub max} = 36.6 kJ/m{sup 3} and H{sub k}/H{sub cj} = 0.83. When Ca was substituted by Ba, pre-sintered powder presents single M-phase structure and close three-dimensional size of grains, resulting in an improved rectangle ratio of sintered magnet. The rectangle ratio of sintered magnet reaches a maximum of 0.93 when x = 0.1. By optimizing process parameters, M-type La–Ca–Ba–Co sintered magnet was prepared with B{sub r} = 445 mT, H{sub cb} = 337 kA/m, H{sub cj} = 420 kA/m, (BH){sub max} = 38.6 kJ/m{sup 3} and H{sub k}/H{sub cj} = 0.95.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

Chemical bonding, phase stability and magnetic property in Sm 2 Fe 17 X 3 (X=H, C, N): A first-principles perspective

As a promising alternative to Nd–Fe–B magnets, the critical rare earth free Sm 2 Fe 17 X 3 (X = C, N) exhibits potential for high-performance magnets. However, their poor phase stability remains a major obstacle to developing bulk magnets. We investigated the phase stability and intrinsic magnetic properties of Sm 2 Fe 17 X 3 (X = H, C, N) using first-principles calculations and chemical bond analysis. The formation energies are negative, while the decomposition energies are −1.53, 0.348, and −0.74 eV per formula unit for X = H, C, and N, respectively, which is responsible for the weak thermal stability. Our chemical bond analysis reveals that the bonding asymmetry between Sm–X and Fe–X interactions creates local structural distortions and degrades the phase stability of Sm 2 Fe 17 X 3 . The project Crystal Orbital Hamilton Population (-pCOHP) analysis indicates that the Sm–X bonding remains positive up to the Fermi level, indicating stable bonding interactions. Here, in contrast, the Fe–X bonding becomes negative near the Fermi level, signifying anti-bonding contributions that reduce structural stability. Interstitial atoms X expand the lattice and enhance Fe magnetic moments, but Fe–X bonding suppresses neighboring Fe moments. Electron transfer from Sm to X modifies the valence state of Sm and the crystal field at the site, contributing to enhanced magnetocrystalline anisotropy in Sm 2 Fe 17 X 3 . Among the interstitial elements, carbon and nitrogen—with their larger atomic radius and higher electronegativity—induce greater lattice expansion and form stronger bonds with neighboring Sm and Fe atoms compared to hydrogen. Consequently, Sm 2 Fe 17 X 3 (X = C and N) exhibits better phase stability and significant improvement in magnetic properties.

Chemical bonding↗

Structural and Magnetic Properties of Fe-Doped Mn{sub 2}O{sub 3} Orthorhombic Bixbyite

There is renewed interest in non-perovskite AB O{sub 3}-type compounds owing to various functional properties such as catalysts, cathode material, and luminescence. The bixbyite compounds have been the subject of intense study in the recent literature owing to their fascinating structural and magnetic properties. In the present work, we have prepared a Fe-doped Mn{sub 2}O{sub 3} bixbyite compound by a mechanochemical synthesis method and studied structural and magnetic properties. The compound is found to be orthorhombic at room temperature and exhibits two antiferromagnetic transitions at 80 and 30 K. Signatures of strong magnetic frustration coexisting with the long-range magnetic order are observed in this sample from the magnetization measurements. The results of our preliminary studies are presented here in light of the current interest in search for novel physical properties in non-perovskite AB O{sub 3} compounds.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

Influence of oxygen partial pressure on the microstructural and magnetic properties of Er-doped ZnO thin films

Er-doped ZnO thin films have been prepared by using inductively coupled plasma enhanced physical vapor deposition at different O{sub 2}:Ar gas flow ratio (R = 0:30, 1:30, 1:15, 1:10 and 1:6). The influence of oxygen partial pressure on the structural, optical and magnetic properties was studied. It is found that an appropriate oxygen partial pressure (R=1:10) can produce the best crystalline quality with a maximum grain size. The internal strain, estimated by fitting the X-ray diffraction peaks, varied with oxygen partial pressure during growth. PL measurements show that plenty of defects, especially zinc vacancy, exist in Er-doped ZnO films. All the samples show room-temperature ferromagnetism. Importantly, the saturation magnetization exhibits similar dependency on oxygen partial pressure with the internal strain, which indicates that internal strain has an important effect on the magnetic properties of Er-doped ZnO thin films.

36 MATERIALS SCIENCE↗

Electronic and Magnetic Properties of Lanthanum and Strontium Doped Bismuth Ferrite: A First-Principles Study

While bismuth ferrite BiFeO 3 (BFO) is a well studied multiferroic material, its electronic and magnetic properties in the presence of A-site dopants have not been explored widely. Here we report the results of a systematic study of the local electronic structure, spontaneous polarization, and magnetic properties of lanthanum (La) and strontium (Sr) doped rhombohedral bismuth ferrite within density functional theory. An enhanced ferroelectric polarization of 122.43 μ C/cm 2 is predicted in the uniformly doped BiLaFe 2 O 6 . We find that substitution of Sr in the A-site drives the system into a metallic state. The nature of magnetism arises mainly from the B-site Fe exhibiting a G-type antiferromagnetic ordering. Our study finds that upon dopant substitution, the local magnetic moment is decreased and its magnitude is dependent on the distance between the Fe and the dopant atom. The correlation between the local moment and the distance between the Fe and the dopant atom is discussed.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

Magnetic Properties of Iron-Doped Bi{sub 2}Se{sub 3}, a Topological Insulator

We study the dc magnetization of a Bi{sub 1.94}Fe{sub 0.06}Se{sub 3} single crystal in the temperature range of 1.9 to 400 K in applied magnetic fields up to 70 kOe for two sample orientations in the applied field. We register three magnetic phase transitions and observe considerable anisotropy of the magnetic properties. The coercive force varies with temperature in a nonmonotonic manner. For the sample in a paramagnetic state, we estimate its magnetic moment per iron atom; its Curie–Weiss temperature is found to be negative. Arrot–Belov plots are constructed.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

Emergent magnetic properties of biphase iron oxide nanorods

We report on the magnetic properties of biphase iron oxide nanorods (NRs) consisting of ferrimagnetic Fe 3 O 4 and antiferromagnetic α-Fe 2 O 3 phases. Annealing as-prepared NRs at 250 °C for 5h, significantly improved the crystallinity of the Fe 3 O 4 phase and enhanced the volume fraction of the α-Fe 2 O 3 phase. Magnetometry data consistently reveal these two magnetically distinct phases, which are not in proximity to each other but separated by a region of disordered spins giving rise to enhanced magnetization at low temperatures when the sample was cooled down from 300 K in the presence of a 1T field to 10 K. This phenomenon which is also known as the pinning effect is much more pronounced in the annealed sample, resulting from the increased volume fraction of the α-Fe 2 O 3 phase which could strengthen the interfacial spin frustration between these two phases and enhance the density of disordered spins at the interface.

36 MATERIALS SCIENCE↗